4. Any ideas on when these Sxs's were made ?

H&A was out of the sporting arms biz by 1915 when they took on a contract to make MAuser rifles for Belgium. That project failed and so did the company,,bankrupt by 1916. MArlin bought them out and made BAR parts along w/other things in the old factory till the end of WW1

Pre-1898 H&A arms are marked Hopkins & Allen Mfg Co.
The company nearly failed at that time, but was reorgnized;
New big wheels, no more bicycle mfg, and the Merwin & Hulbert line of pistols was dropped.

Reorganized,,Post 1898 are marked Hopkins & Allen Arms Mfg Co.

The SxS's are most probably Forehand & Wadsworth Arms guns.
In 1900 the H&A factory burned . Production was moved into the Forehand & Wadsworth plant in MA as it was for sale at the time and purchased by H&A.
H&A continued to make F&W arms, incl their sxs as well as the H&A arms on salvaged machinery from their burned factory.
H&A moved back into their 'new' facitlity in Norwich in '02. Bringing both their H&A and the F&W machinery.

I passed up a very nice H&A marked 16ga one time.Nice original engraving, checkering, damascus finish. Still wonder why I kept on walking! The action looked like the one posted in the link above. The example I saw was not quite as high grade as that one but ws not a 'Field Grade' either. Nice shotgun!
They made some very nice small and medium frame rifles also in sporting & mid-range target styles.