Here is the best place to speak about vintage FF, as we are some nuts of this watch...
Be very careful, as there are a lot of frankenwatches, about the FF...
As always, buy the seller, more than the watch...
Maybe you can post here some scans of the FF you have in mind and some experts, here, like Steve G or Dr Strong, may help you, and I'm sure it will be their pleasure...
I personnaly own a FF or the German Army, a pure beauty with its No Rad Dial...
Best.
Nicolas