Tube rolling for Musical Fidelity Nuvista M3?

I'm not 100% sure,but someone told me years back that they were made by RCA,even if they have different brands stamped on them.

I put some new ones in I ordered from England. I was doing some other things to it at the time so too much time elapsed to be sure but I thought it might have sounded a little better; I don't think it makes the big difference that all tube units see when switching tubes. I would not expect startling differences. Mine were NOS, I want to say Silvania but I could be wrong. Not RCA, although I looked at them also.