4-Speed Identification

I've been searching and searching and I just can't find any coherent information on how to identify whether my 4 speed is an OD unit or not.

It's got some numbers on it but searching them reveals absolutely nothing and there is no list of casting numbers that I can find.

Picking the trans up and looking all around it revealed the following,

Number on the tailshaft
C 133 64A

Shift cover
C-99386

Bearing retainer
C13157

Left side ahead of the cover
C 13303 C

"H A P" stamped opposite each other on the case and tailshaft

I would love to know what gear ratios I have... :burnout: