Digitall 423,

Congratulations on your find.  I enjoy getting old clunker single shots shooting again myself.  Both my #2 Rolling Blocks have the following on the side, in very light stamping:

Patent
May 3 1864
May 7 June 1
Nov 2 Dec 24
Dec 3(1?) 1872
Sept (7?) 1873

There is nothing on the upper tangs of either.  On the lower tangs next to the buttstock screw hole, are the serial numbers, stamped much deeper than the stuff on the side.

Both have a small screw in the left side of the receiver that retains the extractor, which is a vaguely L-shaped piece with a cutout allowing the extractor to ride along the set screw without falling out and an extension on the bottom of the part that engages the shell.  This in turn is engaged by the end of a cut in the breech block, when the latter is nearly wide open, to pull the extractor rearward from the barrel.  I've never seen one with the circular extractor, and neither of mine have firing pin retractors; the pin is just loose in the block and comes back by gravity.

I would surmise that you could reclaim your broken extractor by welding a lump of metal on the rearmost end and filing until it fits in the slot and engages the block as it should.  If not, there is an outside chance that you could get an extractor from a Pedersoli Baby Rolling Block and adapt it to fit.  No guarantees; check with VTI Gun Parts and see by the drawing if it is likely to fit.  I was able to use their version of the sear/breech block spring as a replacement in one of my #2's.  It isn't a really good fit, but it works.

I've also never seen any Remington Rolling Block which has a sight built up from the breechblock itself.  Yours may have been improved by some "talented" amateur.  A common hazard on the clunker trail, and generally more troublesome to get right than almost any amount of wear, breakage or corrosion.

I think the #2 is the classiest-looking of all the Rolling Blocks.