The British Army start using ID discs in 1907 when it was decided that all soldiers should wear a single metal tag, with name, rank, number, regiment and religion stamped on it. On 21st August 1914 it was decided to move away from a metal tag to a single compressed vulcanized rubber one which was red in colour.

In the field regulations of October 1914 it stated that “Anyone concerned with burying a soldier, or finding a body after an action, will remove the identity disc and pay book”.

But the powers that be had not taken into account the destructive power of weapons in WWI and had thus allowed a flaw to remain in its guidance relating to the administration of casualties.

By removing the two key forms of identification from a body, the possibility of misidentification of the dead became more likely.

On 24th September 1916, a second disc was introduced and so a soldier now had to wear two compressed fiber discs, one red and one green. Both discs contained the same information but a change in the rules covering the handling of bodies said that the green octagonal disc should remain with the body.   

As not everybody trusted the quality of the  vulcanized tags, some soldiers made other ones of stainless steel, aluminium or even silver, material that would not disolve that easy as the original ones issued.

I have placed examples of them on the right.

The Identification Tag was first introduced 20 December 1906 by General Order # 204, which described it as follows: … an aluminum Identification Tag, the size of a silver Half Dollar, stamped with the name, rank, company, regiment, or corps of the wearer; it will be worn by each Officer and Enlisted Man of the Army whenever the field kit is worn; it will be suspended from the neck, underneath the clothing by means of a cord or thong passed through a small hole in the Tag; it is further described as being part of the uniform…” This Identification Tag will be issued by the Quartermaster Corps, gratuitously to Enlisted Men ant at the cost price to the Officers.

The “sole” purpose for wearing “Dog Tags” was to enable positive identification of a casualty or remains, and to make a difference both for the families and the authorities, should the person end up as being ‘known but to God!’

Following a number of inquiries related to Identification Tags and with the purpose to help collectors & re-enactors complete their WW2 impressions correctly, we thought it might come in handy to say a few words about “Dog Tags” worn by Medical Personnel, e.g. Army Nurse Corps – Hospital Dietitian – Physical Therapist – Contract Surgeon. They all used specific prefixes and numerals on their Identification Tags, and while dealing with the subject, we thought some additional data on the subject of “Dog Tags” in general, would also be welcome …

20 December 1906 > official introduction of a SINGLE Dog Tag (ref. GO # 204)

06 July 1916 > official introduction of a SECOND Dog Tag, i.e. a full pair is now available (ref. C1, GO # 80 + C2, GO # 58)
12 February 1918 > official introduction of ARMY SERIAL NUMBER (too many identical names e.g Brown, Jones, Williams)
01 December 1928 > Dog Tags are now officially part of the uniform and must be worn at all times (ref. C1, AR 600-40)
01 October 1938 > start of tests related to the introduction of a new Identification Tag (introduced in 1939)
TAG, IDENTIFICATION, M-1940 – Stock No. 74-T-60 > official stocklist number + nomenclature adopted in 1940
NECKLACE, IDENTIFICATION TAG, WITH EXTENSION – Stock No. 74-N-300 > official stocklist number adopted in 1943. Length 40 inches. In 1942, the first tag is to be suspended on a necklace 25 inches in length, while the second tag is to be fixed to a separate necklace extension not further than 2 ½ inches under the first one – first models of tag holders were in cotton, plastic, nylon, rayon, the official “double-J” metal necklace was only introduced in 1943 (with hooks & catches) the bead type (initially sold at PXs) quickly became very popular and available in case of loss and gradually replaced the 1943 issue, it was made out of 2 lengths of stainless steel, of approximately respectively 28 inches and 6 inches in length, easy and practical for general use.
TAG 2” X 1 1/8” > official dimensions: 2 inches (long) x 1 1/8 inches (wide) x 0.025 inches (thick). Rectangular form with notch at left (to position tag on the embossing machine) small rolled outer edges, and a single hole (dia 1/8″) for the necklace. Early types were manufactured in Monel and had a capacity for 5 lines of text, providing 18 spaces per line (ref. Cir # 151, AR 600-40, WD, 12 Dec 40). The official Dog Tag required the following information: Name, Service Number, Date of Tetanus Inoculation, Blood Type, Person to Notify, Religion. US Army Spec No. 34-18, dated 15 February 1939 called for production of a thin metal copper-nickel alloy identification tag (i.e. Monel). Because of the high content of copper, Monel Dog Tags had a yellow/brass color (due to wartime shortages, nickel-copper was sometimes used, whereby Monel tags looked more like ‘silver/white’ metal in lieu of yellow). Steel and stainless steel were also in use.
As early as 1941 AR indicated that any member of the US Army was to wear the Identification Tags when in the field or on garrison duty. On 29 December 1942, the overall texts were amended to include that every soldier was to wear his Identification Tags even when dressed in civilian clothes (during passes or furloughs).  (WW2 US Medcal Research Centre)

The format and the information on US WW Dog tags changed four times between December 1940 and April 1946:

Type 1 December 1940-November 1941

Type 2 November 1941-July 1943

Type 3 July 19430March 1944

Type 4 March 1944-April 1946

Erkennungsmarken (identification tags, and often abbreviated "EK") were issued to all existing members of the Wehrmacht on the first day of mobilization in 1939.

The serial numbers on a tag were called "Erkennungsmarken-nummern" by the Germans and every company-size unit started issuing them with the number "1".  Therefore, since the field units mobilized in 1939 had only just begun to issue tags with their unit names on them, the serial numbers on these early tags should be relatively low-numbered, as we see in the examples above.  Since the 1939-period rifle company contained about 175 men (the full-strength bicycle squadron in the ca. 1939 Aufkärungsabteilung contained 158), the tag numbers on these early tags should be lower than the strength of the unit at mobilization.

Tags were made of several materials, depending on what period of the war they were issued and who issued them.  The earliest tags were made of aluminum, and this material appears to have been common until perhaps 1941 or 1942, when zinc began to become more common.  Zinc remained the material of choice until war's end, even though steel superseded it in some high-volume replacement units during the late summer and fall of 1944.  As you would expect, the use of various materials saw considerable overlapping, with some aluminum tags being issued as late as 1943, especially amongst specialist replacement units or field outfits which would not issue enough tags to have to replace their stocks with tags of a newer material.

There are two variations in the orientation of the stampings, depending on who issued the tag.  For some reason, Ersatz units and many "zone of the interior" units usually stamped their tags so that the bottom of the inscription of each half faced the axial perforations.  In other words, no matter which way you look at one of these tags, one of the inscriptions will be right-side-up and the other will be upside-down.  Field units generally stamped their tags so that both inscriptions are right-side-up when the tag is held with the two neck-cord suspension holes are at the top.  These orientations are not rules, however, they are tendencies; there are sure to be exceptions!

The actual type of stamping also varied.  A few tags are stamped completely in capital letters, but most are stamped in a combination of capitals & lower case letters.  The earlier tags also tended to use larger-sized letters.  Some tags used scribed-in guide lines to help stamp the letters in a straight line, and some do not.  One tag examined still bears pencil marks as guide lines.

According to Wehrmacht regulations, the actualstamping was carried out in a unit's Waffenmeisterei (ordnance section).  In fact, the first tag issued by Füs.Kp.V.Gren.Div.272 (Serial #1), was worn by Heinrich Dietz, the Waffenmeister himself!

French

France issues either a metallic rounded rectangle (army) or disk (navy), designed to be broken in half, bearing family name & first name above the ID number. 

They were essentially identical. A set of three, 2 smaller worn around neck and 1 larger worn as a bracelet. The larger one is perforated with near identical information on the smaller segment. Only to be detached in the event of death. The info is Military district, Name, service number (unique to military district, however not to army as a whole) and class year (the year eligible for service, IE year you turn 20 and this is NOT birth year!)

Dutch

In 1905 the first identity plates were put into use in the Dutch army. Such pictures were already known abroad. One of the inventors is the field geologist Doctor Gustaaf Adolf Frederik Molengraaf who became involved in the peasant war. As the organizer of the Identity Office, which exchanged data between the two warring parties about prisoners, wounded and killed, Molengraaf devised the Dutch recognition plate

In 1917, plates of zinc were put into use in the Dutch army, executed in two models, A and B. These models consist of two parts; one part remains on the body of the fallen, the other part is taken for identification. the Model A consisted of two rectangular plates connected to each other by a cord. This model is replaced in 1923 by Model B, which has the shape of the current identity plates; a rectangular plate with a narrow slit in the middle so that it can be broken in two. Each part has the same information. In the event that a soldier was killed, the upper part remained on a cord around his neck, or if his head was mutilated, in his boot, and the lower part was broken off and handed in to the officer in question. In the first instance, they were described by the Dutch soldiers with white ink, which was prepared in the regimental pharmacy. Later the name, unit and blood type were stamped in with steel letters.

The form of immatriculation that arose in the First World War remains in use until mid-1921. It is then switched to the slightly larger immatriculation plates that remained in use until 1940.

The form of immatriculation that emerged during the First World War turned out to be unclear and tenable in practice during the war and especially just afterwards. A better organization is necessary. In the regulations of 10 June 1921 a completely new system of immatriculation is worked out for soldiers and non-commissioned officers. This remains in use until 1940. This method is based on the fundamental principle that a soldier always keeps the same basic number. This basic number is always composed on 2 groups of digits. The first three refer to a unit or force (which can directly engage soldiers), the last group of 5 digits is the sequence number.

This publication emphasizes that the new numbering applies immediately and that the quartermasters must ensure that with regard to the soldiers who have already been registered, the three police figures on the left are added to their serial number.

During World War II, the Soviet Union did not issue dog tags. Instead, they opted for a cylinder with a piece of paper in it providing the details. They began issuing oval tags after the war ended. 

At the beginning of the Soviet-German war, they introduced tags, so-called ‘suicide tags,’ in ebonite capsules, which contained a piece of paper with the soldier’s personal data. However, the tags were not very hermetic. There were strange superstitions in the Red Army, the soldiers thought that if they wrote down their information on the paper, they would be killed. They carried needles, thread, other small things in those capsules. In the beginning of 1942, they introduced a ‘Red Army’ booklet, which, of course, cannot be preserved.