You're aren't the first to blame me for influencing purchases, and I know you've done your share as well. ;-) Excellent pick-up Anders! And welcome to a very exclusive club. :-!Dennis, it's your fault.;-)
That is an early 60's Conquest Calendar with a caliber 291 inside. The serial number could be from late 1959 at the earliest. Longines only made them with the date at 12 for a short period. The date switched to the 3:00 position after only a couple years at most. There was a flaw in the design of the shape of the original crowns used on two models - the date at 12 and power reserve versions. They were scalloped like this:care to share some details?