Not a Broder.
The Standard Catalog of Baseball Cards calls them "1909-10 German Baseball Stamps" because of a marginal annotation "Made in Germany" found on some stamps. It's a 36 player, 42-stamp set.
Searching images it is clear there are two parallel sets. One normal image. And one mirror image/text believed to be used as tattoos/transfers.
The catalog doesn't list the teams. Old Cardboard has some teams listed. So it'll take some research to complete a checklist. Or more internet searching to find a completed checklist.
UPDATE: I've researched all the teams and checklist is ready.
Someday my cards may double in value and then be worth half of what I paid for them.