I have some photos of my grandfather's during WWII and the occupation in Japan (1942-1949???). They are from all different places in Japan and were taken at different times. I wanted to know if there is anything I can find out from the numbers on the back of the photos (I would be grateful for ANY information). They all have the same numbers so it is probably regarding the printing of them. The numbers are: 773R stamped (typed?) in purple ink and the photos are printed on Velox photo paper.
The number is called a "twin check". A number was assigned the roll of film. Usually assigned in the order opened at the sorting table. The prints made from that roll are given the same number. The 3R stands for 3X enlargement rectangular. This is likely a 3 1/2 x 5 inch print.