Stamp box directory
EKC stamp box: dates and marks
If the stamp box on the back of your real photo postcard carries this mark, the paper's production window narrows the card's date. A stamp box dates the paper, not the photograph — read the range below as “no earlier than,” and let a postmark set the latest possible date.
Standard mark
circa 1930s–1950
Sources disagree here: start year differs widely: 1930 (S6 detail page), 1939 (S5 chart), 1940 (S1/S2), 1945 (S3); we publish the widest defensible span. We show the consensus range rather than false precision.
Ranges cross-checked across: the2Buds.com chart, as republished by Sports Collectors Daily, 'Dating Vintage Real Photo Postcards'; SABR Baseball Cards Research Committee, 'Dating and Authenticating Real Photo Postcards' (2017); Postcards Everywhere collector chart (2010); Playle's Directory of Stamp Boxes (playle.com, frozen reference; marketplace closed 2020); Playle's detailed stamp-box directory pages (playle.com/realphoto/photoa.php, photod.php; image-keyed, contributor-verified; fetched 2026-07-18). Approximate by nature — see methodology.