From the rear of the display storage cabinet these pieces reappear. They have been in my possession since the early 80s and when I purchased them at an estate sale memories of the same things from when I was a child playing at my grandmothers with the same thing flashed. With that in mind I can safely date them back to the early 50s or before.
The 13 pronged pieces have raised letters on each side making up the complete alphabet. As photos indicate use and age have resulted in various issues as to lettering paint.
I last used these in 2 small storefront display windows of a local jewelry store back in the early 80s where the message was that both antique / estate and new pieces were being featured.
I have no clue as to material of black squares as to Bakelite or plastic or ???
The plastic holder measures 1 7/8” x 9” x 1/2”
The lettered pieces with prongs measure 1.5” x 2” x 3/8”