RB gearbox and rear diff

Is there any differences on the casings of an RB gearbox and rear diff?
I remember talk of different fins on a rear diff casing but cant remember what diff that was.
How could i tell if its an RB gearbox without taking the casing off. Besides driving the car?
While the gearbox is on the car...
Same goes with the rear diff.

I font know the answer but can't you take it for a drive? Think rb boxes top out at 120ish mph?

No mot or tax on it at the moment mate

Rear fins are different on a uk sunny stu helps with cooling on the uk model

Diff that is

My max is 125/6 mph on 5th limiter but I'm running 18s
Assume I'm on an RB.

RB box casing exactly the same only thing different is gearset raitio, transferbox & rear diff all same.
May have different numbers on box that could identify RB from RA box .