Patek Philippe. A rare and early 18K gold openface perpetual calendar keyless lever chronograph watch without moon phases

With Patek Philippe Extract from the Archives confirming production of the present watch with guilloched case back and engraved J.A.A.B monogram on the back in 1890 and its subsequent sale on 13 February 1882.

This watch is a very rare example of one of Patek Philippe's early perpetual calendar watches, its most evident characteristic the absence of the moon phase indication usually found in these timepieces, either in form of a fourth subsidiary dial or combined with a calendar indication or constant seconds. It is furthermore believed to be the only watch of this type known to exist to date featuring the additional function of a chronograph.

The only remotely comparable early openface perpetual calendar watch without moon phase, however with four subsidiary dials and without chronograph, is illustrated and described in Patek Philippe Museum - Patek Philippe Watches - Volume I, p. 278, Inv. P-312.

Adrien Philippe's perpetual calendar mechanism was patented in 1889 but was already in use before, such watches however often featured experimental systems which were improved over the years.