Scarce Early 20th Century Milton Bradley Parish Number Tablets Set

I can find no other set of these out there anywhere, and pretty much no reference for them, except a few mentions of "number tablets" used for reaching simple math, produced on wood and cardboard in the later 19th and early 20th century, which is around when Milton Bradley produced these. Each of the 20 cards here is double sided (my photos show one side then the other of each, in batches.) I honestly do not know how they were used--but certainly the colorful dots and varied arrangements lend themselves to counting exercises, and one could match cards with the same numbers of dots arranged in different configurations, say. Now, I'd make up all sorts of games to play with them. And really I just love early Milton Bradley leaning materials of all sorts and will always scoop them up--and these are definitely scarce ones.. 

 Box 6 1/4" x 3 1/2" x 1 1/4". General wear to the box but cards in very good condition. Twenty double sided cards--I can't say if there were once more as I can find no reference for these.