Volvelles were used to solve problems concerning the calendar, tide tables, the rising and setting of the sun, moon, stars, and the positions of planets. This example consists of three parts - an engraved circle with 31 divisions, into which two separate pieces of engraved paper are attached with a red satin ribbon. The inner piece, with a decorative engraved center, is marked with twelve months, and rotates around the circle, and the central piece, marked index, rotates as well. An extremely interesting apparatus, more amazing for the fact that it is still fully functional. The verso has related text.

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Condition: B

Light foxing and damp stains in the margins.