In 1948 together with ETA with their brilliant chief engineer Heinrich Stamm Eterna developed and launched a fully oscillating bi-directional autowinder (Eterna calibre:1194) unlike other earlier oscillating weight designs from Rolex and Felsa the Eterna oscillating weight was mounted to a ball bearing and coupled to a clever reverser wheel system that allowed smooth manual winding well as efficient autowinding.
By 1949 the larger Eterna calibre: 1237 series was manufactured specifically for mens watches and came in several size variants with and without date complication. There are a few suffix variants related to rotor and shock protection designs that where changed during it’s production run most notably the shock protection that changed from T to UC already in the first year of production. Another modern modern feature was the centre second design on all models. These movements where produced up until 1953 when they where replaced with the new calibre 1413 series.
Eterna calibre 1247 variations:
1247/1237: 12.5”’
1248/—-: 11.5”’
1249/1239: 13”’, rotor same as 13.5”’
1253/1243: 13”’, rotor same as 12.5”’
1254/1246: 13.5”’
Eterna calibre 1247-1254 series:
- Made: 1949-1953
- Made in Switzerland
- Power reserve around: 42h
- 17 Jewels
- 18000 B/A
- Lift angle 52°
- DM 27.7mm-30.6mm
- H 5.9mm
Surface finish is very fine with beveled edges. Movement is rhodium plated gilt infilled lettering. Oscillating weight have two main designs the first being E shaped and the other D shaped. The E shape are either gilt or rhodium.
Top surface finish on plates: 9 Points
Surface finish on screws: 9 Points
Surface finish on ratchet and ratchet wheel: 7 Points
Movement Jeweling: 5 Points
Movement design innovation (1949): 10 points
The Eterna calibre 1247 series base plate has a nice finish with perlage decoration . The winding and setting mechanism feels nice to operate. Gear train has a exellent finish.
Base plate finish: 7 Points
Setting and winding mechanism: 7 Points
Gear-train finish: 8 Points
Date change snappiness: 6 Points*
Movement durability: 7 Points
The 1247 series base movement is directly related to the first generation of direct sweep second movements (Eterna calibre: 1078) and does not require any tension springs to avoid a stuttering of the sweep second hand.
Eterna had their own shock protection that greatly influenced Citizens later “Para Shock” system.
Bi-directional automatic device is well made and robust.
Autowinder mechanism: 8 Points
Eterna calibre 1247 series will keep exellent time when in good condition.
Accuracy: 8 points
+2 points for chronometer version*
Power reserve of 42 hours is good.
Power reserve: 7 Points
Eterna calibre 1237-1239-1243-1246-1247-1248-1249-1253-1254 series points summary:
Surface finish on bridges and top side of base plate: 8-9
Surface finish screws: 9
Surface finish on ratchet and ratchet wheel: 7
Movement Jeweling: 5
Movement innovative design for ca 1949: 10
Base plate finish: 7
Setting and winding mechanism: 7
Date change snappiness: 6
Gear-train finish: 8
Movement durability: 7
Total bonus points: 0
Autowinder: 8
Accuracy: 8-10*
Power reserve: 7
Grand total: 91-100
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