Rega Planar 3 Tonearm Question


I have a Rega Planar 3 that I bought in the late 80s which has gone unused for the most part since then. It's now time to sell it to someone who can enjoy it, I'm trying to figure what tone arm I have on it. My recollection is that I bought whatever came with it. Would that be the RB300? I don't see any markings.

Many thanks.
engelz