Stamp box directory
CYKO stamp box: dates and marks
Cyko paper was made by Ansco and was widely used by studio photographers; a crisp professional portrait on a CYKO back is a common find.
Standard mark
1904-1920s
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); Postal & Paper, 'Dating Postcards by the Stamp Box' (2026); 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.