My knee-jerk reaction is save your money and wait for a better one (in light of the unfortunate condition of the finish). That said, you may have a rather loooooooooooong wait. While these guns are not rare, they're scarce in this country, the bulk of them having been shipped to Europe and South America (so I'm told by Jinks).
I have one, a 6" Target #22530, shipped June 7, 1910. It is the only one I ever encountered for sale. Standard guns may be more plentiful. Mine is one not marked as Model of '91 (simply the one line barrel address). Gary Lowe, who has forgotten more than I know about these things, opines these "one line" guns (with matching numbers) are very rare. I suspect those carrying the one line address do so for no special reason. Maybe the regular Model of '91 stamping die was broken that day---so they used another one. He'll be along to help you sooner rather than later. If Terry Wagner, who specializes in these revolvers and their single shot offspring sees this, he's a walking encyclopedia on the topic.
You have the SCSW, so you know the values published there. While the values shown in SCSW-4 have increased substantially over those in SCSW-3 for higher condition guns, those for lower condition examples have not-------which is pretty much the reason to take a pass on this gun.
My bottom line is the same as the top----wait for a better example.
Ralph Tremaine
As an aside, while mine letters as shipped as a target gun, the prevailing wisdom is it wasn't born that way. The latch/sight isn't numbered. THAT scared the wits out of me at the time, but I bought it anyway (at an attention getting price)----and sweated out waiting for the letter. Jinks opines all this came about thus: An order was received for a 6" Target. They had none in inventory, and were left with the options of declining the order or making a gun. So they made one. A standard gun was taken from inventory, given to the Service Department with instructions to make a target gun. They swapped the sights, and voila----a target gun!! Given the Service Department works on one gun at a time, and no batch finishing was involved, there was no need to number the latch---so they didn't. (They may have swapped the grips at the same time. They too are not numbered, so we'll likely never know.)