ETA was one of the three firms “chosen” to develop advanced automatic watch movements by Ebauches SA, thanks in part to their history with Eterna. The chief designer at ETA, Heinrich Stamm, had created many of the company's important watch movements, and was famous for the Eterna-Matic line of watches.
When it was introduced, Cal. 1237T was the first full-size movement with a ball bearing rotor. This five-ball design would become the logo of the Eterna watch company. The family was also the first ETA/Eterna movement with a free-rotating central rotor, unlike the bumper rotor in its predecessor, Cal. 1158/1159.
Although thicker than preceding and succeeding movements, this family is still quite thin at 5.9 mm. Most models have 17 jewels, though later versions have a 21 jewel option. All operate at 18,000 A/h and have 42 hours of power reserve.
This movement family includes 11.5 ligne, 12.5 ligne, and 13 ligne variants.
Cal. 1247 one of a family of automatic movements.
All movements use suffix “U” to signify Eterna-U shock protection or “T” to signify “Eterna-T”. Movements with the suffix “C” indicate a modification to the design.
- Eterna 1248 - (1949) 11.5 ligne
- Eterna 1247 - (1949-1954) 12.5 ligne
- Eterna 1237 - (1949-1954) date
- Eterna 1254 - (1949-1954) 13.5 ligne
- Eterna 1246 - (1949-1954) date
- Eterna 1249 - (1949-1954) 13 ligne
- Eterna 1239 - (1949-1954) date
- Eterna 1253 - (1949-1954) 13 ligne
- Eterna 1243 - (1949-1954) date