ID Tags "Dog Tags" - Basic shapes 

There exists 6 basic shapes of USMC "Dog Tags" :

• A - circular perforated at one side, size : of a silver half-dollar
• B - circular perforated at each side, size : of a silver half-dollar
• C - oval perforated at one side, size : width 1.25 inches (3.18 cm), length 1.5 inches (3,81 cm)
• D - oval perforated at each side, size : width 1.25 inches (3.18 cm), length 1.5 inches (3,81 cm)
• E - rectangular with rounded end and notch, size : width 1.125 inches (2,86 cm), length 2 inches (5,08 cm)
• F - rectangular with rounded end, size : width 1.125 inches (2,86 cm), length 2 inches (5,08 cm)

• First officially prescribed – 1916
• Material used – Aluminum
• Number of Dog Tags – 1 or 2
• Dog Tag chain – woven cloth cord, wire in cloth sleeve and etc.
• Dog Tag marking – etched and stamped
• Side one – stamped personal data
• Side two –
  • Empty or
  • Etched print of the right index finger or
  • AEF serial number ( since 1918 ) *

* Notice - The Marines assigned to AEF (American Expeditionary Forces ) in France during WW1 used Army "Dog Tags" of shape "A" and "B". In Marine Corps Manual of 1921 is stated : .... has authorized the use of the Marine Corps identification tag until the exhaustion of present supply, after which the tag in the Navy regulations ( tag of "C" shape ) will be used.  In the inter war period and at the beginning of the WW2 the dog tags were not standard issue. In Marine Corps manual of 1940 is stated " .... ID tags will be issued "in the time of war or other national emergency ....". 

Stamped information : Officer’s Dog Tag

• Initials and Surname
• Rank and date of appointment in numerals denoting month, day and year
• Company ( since 1917 )
• Regiment or Corps ( since 1917 )
• USMC

Stamped information : Enlisted Dog Tag

• Initials and Surname
• Date of enlistment in numerals denoting month, day and year
• Rank ( since 1917 )
• Company ( since 1917 )
• Regiment or Corps ( since 1917 )
• USMC

ID Tags "Dog Tags" - shape "C" and "D" ( 1921 - early 1950's )

• First officially prescribed – 1921 ( originally U.S. NAVY "Dog Tag" )
• Material used – Monel metal * or corrosion-resistant material ( brass, stainless steel and etc. )
• Number of Dog Tags – 2
• Dog Tag chain – Monel wire in cotton sleeve, Monel chain, steel cable in plastic covering and etc.
• Dog Tag marking – early issue examples etched **, later one stamped
• Dog tag of shape "C" - first prescribed – in Marine Corps manual of 1921 ( perforated at one end )
• Dog tag of shape "D" - first prescribed – in Marine Corps manual of 1940 ( perforated at each end )

* Notice - Monel metal is corrosion-resistant alloy of nickel and copper, with small content of iron and manganese

** Notice - The early issue Dog Tag had on side one etched hand-written personal data and on side two etched right index print. 

Stamped information : this is general format, "Dog Tag" format can differ from unit to unit, see picture bellow which shows very different forms of "Dog Tag

• Line 1 : Surname
• Line 2 : First Name & Initials ( or just Initials )
• Line 3 :
  • Officer's rank or 
  • Man's Service number, Religion preferred in prefixes only : C - for CATHOLIC, H - for HEBREW and P - for PROTESTANT
• Line 4 : Date of tetanus shot application with T prefix - T - 8 / 40 and Blood Type - A, B, AB or O
• Line 5 : USMC or USMCR

ID Tags "Dog Tags" - shape "E" ( 1940 - 1959 )

• First officially prescribed – 1940 ( originally U.S. ARMY "Dog Tag" M-1940 ) *
• Material used – Monel metal, Brass or Stainless steel
• Number of Dog Tags – 2
• Dog Tag chain – Stainless steel chain - beaded style
• Dog Tag marking – stamped

* Notice - during WW2 the standard issue "Dog Tags" used by USMC were tags of "C" and "D" shape, the wider use of U.S. ARMY M-1940 "Dog Tag" by Marines started after the end of WW2. On most examples of M-1940 USMC and USN "Dog tags" I had possibility to survey is not stamped date of Tetanus shot application, which was stamped to standard tags of "C" and "D" shape during WW2 and thus these tags should be post or very late WW2 issue. After war M-1940 tag continuously replaced the tags of "C" and "D" shape.   

Stamped information : this is general format, "Dog Tag" format can differ from unit to unit

• Line 1 : Surname
• Line 2 : First Name & Initials ( or just Initials )
• Line 3 :
  • Man's Service number
  • Blood Type

   

• Line 4 : USMC or USMCR
• Line 5 : Religion preferred
  • in prefixes only : C - for CATHOLIC, H - for HEBREW and P - for PROTESTANT or
  • in whole words : CATHOLIC, HEBREW, PROTESTANT

ID Tags "Dog Tags" - shape "F" ( 1959 - 2002 )

• First officially prescribed – 1959 (same for all Armed Services)
• Material used – Stainless steel
• Number of Dog Tags – 2
• Dog Tag chain – Stainless steel chain - beaded style
• Dog Tag marking – stamped

Stamped information : this is general format, "Dog Tag" format can differ from unit to unit

• Line 1 : Surname
• Line 2 : First Name & Initials ( or just Initials )
• Line 3 :
  • Man's Service number ( used till 1965 ) or 
  • SSN - Social Security Number ( used since since 1965 ) and
  • Blood Type
• Line 4 : USMC or USMCR and Gas mask size
• Line 5 : Religion preferred
  • in whole words : BAPTIST, CATHOLIC, EPISCOPAL, HEBREW, PROTESTANT and etc.

Abbreviations used above:

123 45 6789 * Social Security Number
O POS, A POS, A+, A- * Blood Type
NO PREF * No Religeous Preference

Others are listed by name of religion.

TET * Tetanus Shot
T43 * Tetanus Shot and Year
RA12345678 * Regular Army Service Number
L, M, S * Gas Mask Size, L=Large M=Med. S=Small
DOB * Date Of Birth
AKA * Also Known As
NKA * No Known Allergies
NKDA * No Known Disabilities