Lagopus - yes, indeed, and I did contact Gibbs last year. Mark Crudgington was kind enough to provide what information he could. First, my serial number "B 4XX" indicated by the "B", a "brought in gun"....which I took to be a finished barreled action, which was engraved, stocked and finished by Gibbs. Based on the "Not for Ball" and other stylistic indications, he (and 2 other smiths) place teh gun as ~1882. He differed from Kirk concerning the lengthening of forcing cones and opening the chokes; he opined no lowering of internal pressures would result. Last week when I provide him "after" pictures and the belief the barrels were 6 iron Damascus, he replied: "The gun looks very good , well done . The 6 iron barrels are probably Belgian ,by the mid 1880s a high percentage of the tubes used came from Belgium where there was a huge ( and cheap ) cottage industry making Damascus tubes of all qualities , hence Greeners caustic comments in edition 9.
Hope you have fun with your bit of " living" history
Let me know how it goes.
Yours
Mark Crudgington"

So, here is one picture of the receiver "after" the project was completed. More pix to come later.
V/r
Maxey