Bruce,
I am glad you decided to keep your 2 barrel set for posterity. As regards the 20 gauge Francotte....I would seek Larry Brown's advice. Finally, what was your source for dates of production by serial number? I ask because I have an old Francotte sixteen gauge with 2 9/16 inch chambers that I would like to date. Let me know when you price the Francotte 20 ga.....I may be interested. Good luck with yours, they are splendid field guns designed for light loads.
Tom Regal

Luck is the residue of good intention and hard work.