Looking at this Black Dial Polerouter 869113

The crown is not original and it will be hard to source a replacement. Otherwise looks fine, if not a little tired. I would want to see the movement and inside the case back to check for rotor wear given how well used it looks.

The rubbing inside the case back would be enough to deter me.

The crown should be the big chunky type, just like the 204612.

It is the 869115 that has the screw-down crown - a smaller version of the Polerouter Super crown.

Really? A little bit of micro-rotor rubbing inside the case back seems very common on these, and to me not an issue at all. This looks like a very nice example, though not a bombé lugs model.

I do not think it looks tired. Some fine scratches and dings, maybe, which mean it has been worn, as vintage watches have been unless they are NOS. Also, it probably looks better in person. If you like it you should go for it, and try to get the price down due to the crown. You can make a long-term project of finding a correct crown, but I would not obsess over it. There are two ways to consider originality. One is to try to make it look as it came out of the factory, the other is to keep it “honest,” as in, passed down through history. In the second sense, someone wore this watch for many years, had it serviced, and probably a long time ago a watchmaker replaced the crown to keep it waterproof, with an updated UG crown. He wasn’t trying to fool any collectors, that’s just what watchmakers did back then. He didn’t polish it (thank God), so you still have the original finishes and edges. This is never going to be a museum piece, just a beautiful, honest vintage watch with a killer black dial.