In the 1950s, if you wanted to feel the pulse of the time and the market, as a watch manufacturer, you had to have an automatic watch with date window in your collection. It was really in the 50s, when this took off. Nowadays, we admire simple dials without date and even manual wound calibers, but in those days, automatic movements and a date function were the latest fashion.
So it is no surprise that houses like Girard-Perregaux and Jaeger-LeCoultre jumped on that train. By no means were those the first, we have known date complications for much longer and also automatically winding wristwatches but as said, in the mid 50s, they really became the sought after complication everyone wanted to have. So we can look at T.W.O early examples from Girard-Perregaux and Jaeger-LeCoultre.
The Girard-Perregaux Ref 7317 houses the Gyromatic caliber 22 with 39 Jewels, marketed at that time as a breakthrough technology as the Gyrotron design allowed for bi-directional winding. The Jaeger-LeCoultre E 329 on the other hand housed a bumper automatic movement, Cal. 813. There are a lot of similarities but also differences.
Both watches have put some emphasis on the date, GP using a blue print for the date rather than the usual black and JLC decided on a Roulette date with alternating black and white dates. Hop over to the Blomman Watch Report for more details on the JLC E 329. It is probably debatable if the full-rotor winding or the bumper winding is better or more modern. Obviously, the full rotor design has ultimately won the market share, but the bumper winding is also very efficient and provides for that very special feel on the wrist, certainly the romantic choice.
Both cases are similar in size, 34.5mm for the JLC and around 33.5-34 for the GP. Lugs are integrated into the case and while the JLC has a more pronounced bezel, the GP uses some case design tricks to let more light into the dial. Lug width is 17mm. On the GP the lug size should be 18mm, but I fitted a 17mm strap which just seems to fit better due to the tapering lugs.