I recently acquired a unique firearm and I'm looking for any info on it.
It's an 1870 Frank Wesson, serial number 12 (numbered on butt and inside grips).  It's in .38 CF with a 24" barrel.  The barrel has been partially relined with a bore of .358".  The liner stops short of the breech, forming a chamber that's approx 1.9".  The liner is smoothbore.
The barrel "lug" is 3" with a rear sight, and a serial number of #2023.  The barrel itself is 21" long.  The breech measures approx. .375".
That size chamber would most likely take a 38-50 Stevens case (or similar).  
Frank Wesson's factory was in Worchester, MA.  Fewer than 50 pocket rifles were made by Wesson.
Stevens/Maynard was in Chicopee, MA, 42 miles away.  A train joins the two cities.
Stevens made "pocket shotguns".
I guess the question I have is, was this gun a special order - someone wanted a longer shotgun barrel so they took a lug marked #2023,  and attached a longer barrel with a liner.   Or, did a gunsmith rework the gun somewhere down the line?
If it was a more recent alteration, I'm thinking that the .358" liner would have been rifled, and extended to the breech so it would shoot .358" (38 SP).
It does not look like it's been converted from rimfire.

Could we get a pic of the action open close up?

here's mine.
I need a rear sight, they are broken on most I've seen.
They are often referred to as "sportsman's jewell".

the front sight is stock for a 22lr, I don't know if they ever came smoothbore, it seems these medium frame rifles only came in .22 and 32 rf rifled.

First of all, Wesson made "pocket" rifles in several sizes and variations, but most importantly a great many more than 50.

In any case, what you have is a gun that has been almost surely modified rather than factory-made for the explicit purpose of hunting small animals, primarily birds, that were going to be preserved by taxidermy.  It would apparently shoot a .38 "shotshell" that was loaded specifically for that purpose.  The examples of such gun most often seen today - and they are far from common - are based on cheap revolvers.  More than one I've seen had the smoothbore "barrel" simply attached to the stub of the original barrel with a knurl-headed set screw.  This is the only Wesson Spotsman's Jewel I know of that's been so modified.

Bill Lawrence

OK, just hauled out the 3 volume set on Wesson and his pistols and rifles. Battis32, the "New" (1870) Model Pocket Rifle was made in 3 frame sizes and many types. Serial numbers usually started over with the type change. Early frames were brass - iron only appearing in small frames type 5. The large frame was iron and it was the one in calibers up to .44 and with possibly only 50 being made and those in only 2 types. They have no screws on the left side of the frame so can't be yours. The small and medium frames were made from 1870 to 1890 and in 22RF and 32RF. The small frames (.625 frame width) were made in 5 types and production numbered 3700 to 4700 guns. The medium frames (.720 to .760 frame width) were the most popular and had several types with a total production of about 7000. I'm guessing yours is a small frame and then would be a type 5 which was serialed on the butt (1 to ~1500) and had the extra screw on the left for an extended half cock and an iron frame.

Lots of good info.  So, basically, it's a three part gun - the frame (#12), the barrel stub (#2023) and the extra long barrel (the barrel looks to be 1 piece).  I'm thinking that the barrel was relined in .358" to act as a choke.  Why else would it have been relined as a smoothbore?
The frame is centerfire and doesn't appear to have been converted from rimfire.  The Wesson guns I've read about were usually in rimfire.  So, would the original barrel have been a smoothbore?

I know why it existed as a smoothbore - hunting, taxidermy, etc.  My question was, and I know it's all speculation, what type of barrel was centerfire frame #12 originally attached to?  Smoothbore or rifled.  If the smaller calibers were made in rimfire (.22, .32), and the .38 CF guns were smoothbore, then it was probably a smoothbore, simply because it is centerfire.  Why, then, reline it in a smaller bore (.358")?
It appears to me that whoever did the alteration work knew what he was doing; relining the barrel, merging the stub and longer barrel, making the longer barrel.  Was the average gunsmith capable of that?
Again, it's all speculation.

I've seen photos of the work Mr Bly has done attaching stubs/lugs with new barrels - that's why I included the pic of the witness marks on the barrel and lug.  Maybe, at some point, the owner of the gun brought it back to Wesson and asked for a longer barrel.  I can only guess at why it was relined as a .358" smoothbore.