PULLEY ASSEMBLY ID ?

I have a pulley assembly that has so far avoided identification.
the various part numbers etc are-

C90403.
90405C.
88913C/X2.
88366B/X2.
88365C.
B1N.
P78.

There are 2 inspection stamps. 1 is THW 15 in a circle, the other is ZM6, also in a circle.

The pulley is marked D2405 A.G.W/2.

I will hopefully upload some photo’s at the weekend.

Any Ideas ?.

Bob T.