For what its worth I have the:
Mk28 part number L81252-10-03 as Ref No 6A/6669
Mk28B part number L81252-04-006 as Ref No 6A/1170854
Mk28C part number L81252-10-007 (and -009) as Ref No 6A/6379219
Mk28D part number L81252-04-008 as ref No 6A/6379200
Its LRU 9 from the AWG 12 radar fitted to the F4M Phantom. The Opitical Display Unit of the Lead Computing Optical Sight System bolted onto the front to make up what was known as the Command Indicator.