When we cross reference other companies at the exact same time frame? I don't know of any "non" matching serial number special orders. Even "conversions" were given a matching set of numbers when using parts from other guns, even other calibers. There was always a "matching" number given to the modified part from a "Factory" rework. That's all I'm saying. That includes: Colt, Hopkins & Allen, Remington, Bacon Manufacturing Co, later Bacon Arms Co, Starr 44 and 38 Conversions. I've seen Starr Conversions with smooth bores also. "Matching numbers". And those were not even factory reworks! They were sold much later to Spanish Companies and reworked by them. Often having Belgium proofs on them. So who knows.

Anything is possible but you would have to document "proof" of several examples to support any position. Especially since this variation is extremely rare? It's also possible that they were made up by someone wanting to sell leftover parts during a period that shot barrels were common. Who knows??

I've seen Colt dragoons with 12" barrels that were so well done that some collectors also attributed them to being "Special Order". However, close examination shows a distinct line inside the barrel where the two piece barrel was threaded and machine assembled. That's not factory work!

Quality custom work was performed by talented gunsmiths during that period. Barrel changes are one of the most common modifications out there.

Also, the 38-45 Stevens "everlasting" was introduced in 1875. The specs do not match the OP's gun. Bullet diameter is .363, neck of the case is .395, and the base diameter is "huge" at .455. that's a tapered case! That's not what the OP is describing. The spec's he described fit the .358 specs "PERFECTLY". It screams "post 1899 modification"!!!

"Extremely" rare examples of any gun without proper documentation is "PURE" speculation. NON matching "factory" assembled guns? That's a tough swallow guys. NOW adding a two piece construction barrel? Screams "modification". NOT special order. I'm now wondering if these shotguns were a contract modified gun. Find one with matching numbers and I'm on board.

All of the known Frank Wesson Pocket Rifles were 1 piece construction barrels. That includes my 44 Rimfire "LARGE FRAME". It's "solid" one piece construction. Rifled barrels up to and including 22". Why would you need to make a non matching two piece construction barrel for a smooth bore shotgun in .38 cal?

Why not just machine a previously existing .32 rimfire barrel to a smooth bore .38 and re-number it to match the special order?

Murph