John, I am by no means anywhere near an expert on things like this but after looking at the pictures, I feel that I need to agree with you in that this receiver has been recased. The checkering on the hammer and breach block does seem to have been smoothed out over the years and if they were used that much the finish would be much worn.  I don't like all the pitting either. If those pitts were there when it left the factory that is very poor quality control. If they had developed later in its life, then there should be finish damage in the pitted area. 
JMHO, FWIW
Sam

And, the seller appears to be quite commendable on his honesty.  Here's his reply:

"I am afraid that I cannot verify the history of the gun. The pitting referred to appears to be from impact and not rust and is around the hammer pivot pin. There is some small areas of rust, not unexpected on a 100+ year old gun. You could easily be correct. That said, I recently purchased a Trapdoor which I do know the history of and it has even better finish so it is possible the finish is original. The checkering is worn but not as badly as you see in the picture. So to be as honest as possible consider it a very good refinish. If you are interested I can send a couple of better pics of any area you are interested in such as the checkering or markings."

Striving to present the gun honestly, just lacking in knowledge.  Seems to be one of the good guys, compared to many online sellers!

wishful thinking!

And, I agree, price would be considerably higher if it was a 90% finish gun. (I already have a couple, which is one reason the faux colors jumped out at me so quickly)

This rifle looks like what is, a $650 rifle......