It’s the same muffler that came on the 266XP and some Jonsered models. Same outlet as shown in your picture. The part number will be stamped on the top of the muffler. I did find the other parts I was looking for, thanks for asking.
Yeah there’s a few that look basically identical, main difference is one has a baffle inside the other (501657703) is a hollow can. Also the screws that hold the outlet deflector on are a fine thread rather than a sheet metal type of screw.
I'll get one tonite or in the morning. It has the flared outward style outlet with a spark screen and screws installed. I have at least one that doesn't flare outward but don't know if it's hollow or baffled.
On the last set of photos, the gasket is likely unusable but I'll include it for your own discretion.