The engraving is rather crude if you ask me - not the subject, the same sort of thing was not uncommon in the 17th-18th century. The artistry is just third-rate.
Its not as classy as many nice shotguns its rather pimp if you ask me.
You really need better and more detailed photographs to be sure, but it appears to me that it is certainly not up to the standards of the greatest artisans of the 18th and 19th centuries...but I don’t think it’s terrible work.
Yep, it was very common in France, Italy and even Japan (google "samurai matchlocks"; that'll probably turn up some similar examples).
Not my cup of tea in terms of art, but the Steyr rifles are very nice, even "unadorned".