The numbers are wooden bingo chips off Amazon and I attached magnets to the back that makes it easy to for them to move. (Links at the bottom)
I write on the sheet metal with expo wet erase markers that way the kids can't wipe off.
However after a few months I realized that I wanted to see two months at a time. So back to Home Depot, now I can see three.
This is in my kitchen and it works perfectly. We see it every morning at breakfast.
31 Pc Wooden Black Bingo Chip Set Crafts Scrapbooking 1 Inch https://www.amazon.com/dp/B009XFEPNG/ref=cm_sw_r_awd_Jb51vbP6MWSP7
BYKES Magnets 1/2" Round Disc with Adhesive Backing - 250 Pcs https://www.amazon.com/dp/B007EI8BK2/ref=cm_sw_r_awd_Oa51vbZSA779W