I found one more reference to these tiles, from an old ebay auction on
picclick:
Take a look at these Sun kissed purple late 1800s manganese dioxide glass panes.
These industrial panes measure
5”X5”x1/4”
And are marked
RICE’S ARISTO
with embossed letters.
These panes are where made to be used with lead seams.
I have quite a few of these beauties.
The original auction and its pics are long gone but
picclick still has this thumbnail saved:

Looks like a duck. I'm 99% sure these were in fact ducks (prism tiles). 4"x4" was the common size, but there were also 5"x5". What RICE's ARISTO means is still uncertain, and the toy/sample washboard just muddies the water. It
does look just like the typical washboard of the time, right? The following is 18" x 7-3/4" x 1-1/4"

And here's another:
