A late 17th-Century Bloud-type ivory azimuth diptych dial,

Details
A late 17th-Century Bloud-type ivory azimuth diptych dial,
unsigned,

Face Ia, the upper leaf, outer face: double-lined and "pecked" borders enclosing a circular equinoctial dial calibrated 1 - 12 (twice), surrounding a polar dial calibrated 8 - 12 - 4, with central socket for pin gnomon (cracked, neatly repaired with staple)

Face Ib, the upper leaf, inner face: latitude scale calibrated 10° to 80°, double-lined and "pecked" borders enclosing the brass, triple-disc lunar volvelle, the inner disc with aperture revealing lunar phase beneath, and engraved with decorative motif

Face IIa, the lower leaf, inner face: double-lined and "pecked" borders surrounding the hour ring calibrated 5 - 12 - 7, the compass needle with brass cap, the pierced and decorated, silvered ellipse calibrated V - XII - VII, the printed, paper compass card listing the latitudes and other details of 19 French cities, brass latitude arm in slot (compass glass and string gnomon replaced)

Face IIb, the lower leaf, outer face: double-lined and "pecked" borders surmounted by a "hand" index, enclosing the engraved brass volvelle, the outer date scale surrounding a perpetual calendar square,

the diptych closed by two silver hooks, clasp-covered compartment for pin gnomon in lower leaf edge (pin missing) -- 2¾in. (6.8cm.) long

See Colour Illustration
Literature
Steven A. Lloyd et al. Ivory Diptych Sundials 1570-1750 (Cambridge, Massachusetts, 1992)

Lot Essay

Although Bloud-type dials are difficult to attribute, the present example would seem to have the same printed card as Lloyd's item 64 (an unsigned dial, mid to late 17th-Century), sharing similar spellings of towns (e.g. "La Rochelle", not "Rochelle"), and a similar printed device to the right of the word "Mydy". Although Lloyd describes the card as listing 18 cities, close inspection of the photograph would indicate 19. The engraved starburst and cloud device and the pointers of the lunar volvelle (face Ib) of the present dial also bear similarities to the volvelles on Lloyd's items 61 (signed "Jacques Senecal", mid to late 17th-Century) and 62 (signed "Jacques Guerard", mid to late 17th-Century), particularly the latter. This would indicate components from a common source in Dieppe in the second half of the 17th-Century.

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