1997BlackCS,
FYI. For what it's worth, I'm pretty sure that there are actually two parts missing from the Rear Mech pics you provided; the missing back plate that respondents have already noted and the B-Seal Ring.
The B-Seal Ring is a dish shaped plastic bushing/spacer that fits between mechanism body and the back plate. Have a look at the attached picture. It is the black "washer" seen between the two. It functions as a dust seal and as a contact bushing.
LGF is correct, the STX-RC, Deore, Deore LX, and XT rear mechanisms of that era all used those same two parts.
FYI. For what it's worth, I'm pretty sure that there are actually two parts missing from the Rear Mech pics you provided; the missing back plate that respondents have already noted and the B-Seal Ring.
The B-Seal Ring is a dish shaped plastic bushing/spacer that fits between mechanism body and the back plate. Have a look at the attached picture. It is the black "washer" seen between the two. It functions as a dust seal and as a contact bushing.
LGF is correct, the STX-RC, Deore, Deore LX, and XT rear mechanisms of that era all used those same two parts.
