Cal 51.0

(c): Mars Mountain

ZENITH Quartz cal 51.0 (ESA 9181), ca 1973-1974. Features quickset day (in German) and date. The ESA 9181 was ETA:s first quartz movement. Quartz @ 32.768 Hz controlling a stepper motor. Seven jewels. It does not have sweep seconds as stated on other sites.

This Zenith XL-Tronic has refererence number 01.0010.515, square steel case and a somewhat scratched mineral crystal. At 41 mm wide (excl. crown) and 12,6 mm thick it is a massive chunk of stainless steel on the wrist.

Cal 50.0

(c):Vultures78

ZENITH XL-TRONIC has movement cal. 50.0, an electronically controlled tuning fork movement based on ESA 9162. It has sweep second hand, date quick set and electrical hack feature. It is a 13''' movement with 12 jewels beating at 300 Hz.

This model has been produced in 1.000 pieces between 1975 and 1976.

This tuning fork watch has 20 µm gold plated case and stainless steel back case. Gold colored dial and hands. Date is placed between 4 and 5. It “humms” very nicely and keeps very good time. Tuning fork watches were sort of transition between mechanical and quartz watches and are not produced anymore. They are rare findings and very hard to service, as spare parts are not made anymore. This particular watch was given to someone for 15 years of loyal work at Unger factory in Norway.

Cal 2541

(c): Mars Mountain

ZENITH movement cal. 2541, mid 1970's. Gent's 11 1/2''' caliber squeezed into a ladies watch. 17 jewels, 21600 bph sub second movement. This was the last Zenith manufactured caliber (1966-1975) featuring sub second dial until the Elite caliber came along in 1994.

Cal 2562

(c): Vultures78

ZENITH movement cal. 2562 dates to the first half of the 1970's. Movement is manually wound, has 17 jewels and beats with 28.800 bhp. It has a 50 h power reserve and excenter regulator. This particular watch was dated to 1973. Dial and hands are well preserved and original. Case is 20µm gold filled and back case is stainless steel.

Cal 2552PC

(c): Mars Mountain

ZENITH movement cal. 2552PC, This caliber was produced around 1969 (15 000 pieces made). 23 jewels, automatic movement @ 21600 A/h. It features a date wheel and center positioned sweeping second hand. A later version (2572PC) also features quickset for adjusting the date, as well as a higher beat rate (28800 A/h).

This particular one, made in 1970, runs fine except when it is time to switch date. It definitely needs cleaning and new oil. The rotor seems to have been touching the case as well. I like this watch a lot, I find most models of the Respirator series quite attractive. There are a lot of cool designs from the 70's!