Embossing Company Vintage Color Cubes Large Set, c 1930s antique marbles rather like a vessel shaped

rather like a vessel shaped rock

it would be quite a thing to pour from

I’ve since learned that a hydrometer is used for measuring the relative density of liquids based on buoyancy: you pour liquid into a container

I believe it is 1930s Zanesville (typically unmarked) though am not 100% certain

Embossing Company Vintage Color Cubes Large Set, c 1930s antique marbles rather like a vessel shapedI believe this is the largest set of Color Cubes the Embossing Company, Albany, NY made endless possibilities! These were made as teaching toys, intended to "teach designing, initiative, colors, concentration, symmetry, observation and patience, but have certainly become as popular among adults as children, and iconic design objects. Really fabulous to keep on the table for infinite hours of creative diversion. The complete set of 49 blocks are in