This gun is a made up gun as the Longrange was not made in a 10 gauge. It was made in 1917.

The Longrange wildfowl gun was first made in 1923, and was only made in 12 gauge on Regular frame.
The 10 gauge was made in an Ideal Grade and most came with London Steel barrels. Damascus steel was available until around 1917.
This seller is either not knowledgeable about these guns or is trying to pull a fast one over on some one.

I definitely would not shoot this gun as now the chamber has been lengthened and the wall thickness has to be significantly thinned.

David