Hey, Shep. I can't tell you a lot, but it looks like they are 1918-1930 based on this site:
https://www.playle.com/realphoto/index.php
The stamp box can tell you a lot. There's a lot of other details to help figure out age like the printing, if the sides are separated, if it's stamped, etc.
Good luck tracking down more info on them. Cool cards!