Hi Texcl!
I have (what purports to be) a Joseph Manton SxS shotgun. The barrel rib is inscribed Joseph Manton, Hollis Street, Cavendish Square, London. Both locks are also inscribed Joseph Manton. The serial number is marked on both barrel flats, both breech plugs, both locks, the trigger guard, and the butt plate. At least, that's all I've found.
To complicate matters, Joeseph had a brother John Manton. They were not partners but competitors in the high-end London gun market. A gun by either would be an historic find. Somewhere, I came across a gun (on the web) marked John Manton and Son, looked 1840's to me. So at least one J. Manton had a high quality business passed on to his son.
For what it's worth, I have heard that Belgian knock offs (probably of varying grades), got around Manton's copyright (or tried to) by labelling guns J. Manton. I believe that came from the double gun forum.
Joseph Manton did go bankrupt, as you have written. He did reopen using his name (and may have crashed again). The late history of the firm is shakey.
As I remember, you started looking for a Pedersoli, and then moved this way. I have 2 Pedersolis, and the clearly labelled Manton. The 12 guage Pedersoli is heavy for a game gun, but the 20 swings well. I got it from
flintlocksetc.com, which is the only place I would go for Pedersoli. Is use the 20 for training Spaniels and to shoot skeet, and I like having a gun I can use and not worry about. (I also like having a club that will let me shoot black powder on their regular days.)
I think that there are more than one market for these guns. TOW is probably the most extensive and varied. (on double gun bb I came across a J. Evans in Philadephia who sold guns that he had Jim Purdy run up for him--so there is a probably a good reason why that Evans double at TOW is pricey, whoever actually made it).
Roosevelt and Drake is fun to look at--and they sell guns at those prices. (Clearly, they have access to a "different" market.)
Vintage Double has a couple of percussion guns, including a Mortimer Percussion SxS for $800. (Kirby has guns ranging from about $800 to $18,000. He crosses markets.)
So, anyway, this is some data that you can take or leave.