Here's an old glass prism tile used to provide sunlight in tunnels and basements, etc. Unlisted on "Glassian" website, which is the premier website for collectors of these ancient relics of a bygone era.

This example measures 5" x 5". Has 1 1/2 match head flakes on the outer rim otherwise excellent condition! 2 are available to the first email for only $35 each plus shipping. Thanks!