Good luck finding the needle in the haystack. Here's a RPCC dating guide. Looks like you can narrow it down to 1904-1918.
Quick Reference Real Photo Old Postcard Dating Guide
PAPER Dates Notes
AGFA/ANSCO 1930-1940s
ANSCO 1940-1960 2 Stars at top & bottom
ARGO 1905-1920
ARTURA 1910-1924
AZO 1926-1940s Squares in corners
AZO 1904-1918 4 triangles pointed up
AZO 1918-1930 Triangles 2 up, 2 down
AZO 1907-1909 DIAMONDS in corners
AZO 1922-1926 Empty Corners
CYKO 1904-1920s
DEFENDER 1910-1920 Diamond above & below
DEFENDER 1920-1945 Diamond inside
Devolite Peerless 1950-
DOPS 1925-1942
Du Pont 1945-1950s
EKC 1939-1950
EKKP 1904-1950
EKO 1942-1970
KODAK 1950-NOW
KRUXO 1907-1920s
KRUXO 1910-1920s Xs in corners
MULTISCOPE & FILM CO-WISC. Pre-1909 BADGER
NOKO 1907-1920s
PMO 1907-1915
SAILBOAT 1905-1908 Sailboat in circle
SOLIO 1903-1920s Diamonds in corners
VELOX 1907-1914 Diamonds in corners
VELOX 1901-1914 Squares in corners
VELOX 1909-1914 Triangles: 4 pointed Up
VITAVA 1925-1934
|