Bob, I've noted with great interest your posts in this thread, and applaud your efforts to comply a Francotte body of information. In fact I had been aware of the Griffin and Howe effort, and was disappointed it seemed not to come to fruition. Maybe with time available, you'll be able to complete the project--it would be a great benefit to many.
I saw the numbers above for the later A & F guns that you listed. Strangely, I have a Grade 45E (Eagle) grade Francotte, in pigeon/trap configuration, beavertail, vent rib, single trigger which is marked Abercrombie and Fitch, New York, but bears the serial number 1397! The gun is virtually mint and appears totally original. Can you think of how such a low 4 digit number could be on an A & F gun? Could there have been some sort of proprietary run of guns with a special set of numbers? Any insight would be appreciated. Thanks, Keith