Middleburn Crank Identification

[Urwin]

Can someone deduce what these cranks are? I cant see a model marked anywhere on the cranks. They are square taper and 175 long. RS7?

 

[ishaw]

Re:

I'd say rs3. Rs7 had the lock ring holding on the spider. Anything before rs3 seems to have a flat spider and a few other differences.

 

[My_Teenage_Self]

Seconded. rs3

rs7 look very similar, but have the lockring, not bolts on the spider. I believe the rs7 were the first to be forged too?