https://creativecommons.org/publicdomain/zero/1.0/https://www.rawpixel.com/image/6074284
Closeup of Soda Hall abacus
Closeup of Soda Hall abacus
Closeup of six wooden lower beads and one upper bead pushed against the crossbar, and one upper bead pushed away from the crossbar. Original public domain image from Flickr
Public DomainFree CC0 image for Personal and Business use