Marauder fill check valve o ring

[Blue]

Well after four years and hundreds of fills my Marauder developed a leak from the check valve in the fill assembly.

I wasn’t sure I could even access the inside of the fill assembly because the black thread tape Crosman used on the nipple looked more like some kind of adhesive and I didn’t even know there were threads in there!

I did a little research through old posts on the good old GTA and proceeded to take it apart.  The o ring is for sure toast and seems to be a bit of a mystery as to size and composition and it’s not listed on my cheat sheet of Marauder o rings.

I’m going to go ahead with final cleaning and I’m planning on using a #006 Buna-N 70 for now.

This seems to be a bit of a rare occurrence and I figured I’d add a post so there’s a little more out there for folks with the same issue in the future.

[Motorhead]

Looks like a 006 to me just not Poly as was the original.
can't say I remember that type fill foster fill & check valve as OEM ?