There are three basic models of the Subaru Centre Differential.
Ths 5MT Model 38913AA10X of which there are three sub-varients 38913AA100, 38913AA101 & 38913AA102
The 6MT model used in Spec-B gearboxes of which there are two sub-varients 38913AA112 & 38913AA200
The 6MT model for Cable Shift gearboxes 38913AA230
For the 6MT Spec-B units 38913AA112 has the drive gear fitted for the internal oil pump & 38913AA200 has had the gear deleted for the updated gearboxes without oil pump
All the 5MT models are interchangeable, they will all work in any Phase 2 5-Speed gearbox application
38913AA100 and 38913AA101 has the 'spiral circlip' - which is reknowned for dislodging from the body of the centre diff and jumping into the transfer gears, usually at great cost to the owner.
The horrible spiral circlip was deleted with the 38913AA102 version and the 'C-type' circlip used in the 6MT centre diffs was introduced on the 5MT units.
Like with the EJ25 NA head gaskets, it took Subaru a long time to recognise that the design had an expensive failure mode issue and introduce an effective known countermeasure
See the pictures below.
The centre diff is fitted with the C-Type circlip and comparison between the spiral circlip (left) and the C-Type circlip (right) is shown below.
CorgiWerx only build their 5MT centre differentials to the 38913AA102 specification with the C-Type circlip.
All CorgiWerx centre differentials have the C-Type circlip.