Platinum Watch no. -

Case: Platinum Emile Vichet case (key 23), s/n; 417950 Dial: long signature engraved enamel two-tone Stern freres dial Movement: s/n; 860820, Caliber 17 ligne, movement signed Patek Philippe & Co, Geneve Swiss, Eighteen (18) jewels, Three (3) heat, Cold, Isochronism, Adjusted five (5) positions, No. 860820. Provenance: 1928 - Niton, Geneve (still validating, ebauche and/or finished by Niton, Piaget or ?) 1928 - Patek Philippe & Cie., Geneve 2023 - Instagram member itsbeenalangeday Early reference 652, sold in Brussels, 1939. Notice; we know for sure, both Niton and Piaget finished these "pre-caliber 17-140" type of calibers for Patek Philippe, with movement serial numbers 860.XXX. In the 20s-30s Patek Philippe bought about 30 movements from Niton, not all the same caliber. Why? My hypothesis are; at the end, every respected Haute Horlogerie, like Patek Philippe, produced (at least) one in-house caliber. And so it happened after the Sterns bought Patek Philippe in 1932. Patek Philippe used these high end calibers from Niton but also from Piaget as an example and experimented with to eventually produce their own in-house caliber like 17-140 and 17-170. This caliber is similar to these Patek's; No. 860.868 (Ref. 618) case No. 613.681, caliber 17 14/12''', according to Patek's archive, made in 1938 No. 860.820 (Ref. 652) And this Niton's; No. 3000 (Niton movement serial number, made for Oscar Fresard) And slightly different to these Patek's (caliber design by Henri Hofer, deposited April 29, 1926); No. 860.568 and case No. 210.114 No. 860.571 and case No. 210.108 No. 860.572 and case No. 210.110, according to Patek's archive, sale on October 25, 1940 No. 860.590 and case No. 616.132 (made in 1937, sold June 30th, 1941) A L'Emeraude movement serial number