The following info appeared in "Old Hickory News", the newsletter of the 30th Inf Div.

Dog tags evolved during WWII to 4 types:

Type I was used from December 1940 to November 1941

Type II was used from November 1941 to July 1943

Both bore the soldier's name, serial number(ASN), and next of kin's name and address.

Blood type and religious affiliation were added in the later months to type II

Type III was used from July 1943 to March 1944 and dropped the next of kin, and added blood type and date of tetanus shots

Type IV came into use in April 1944 and differed from the Type II in that one's surname was now listed first, followed by first name and middle initial