Sorry missed that. The problem with that era of speakers is that most manufacturers used the same parts (frames and magnet structures ; there were some more distinctive, but not reliably so). Cones varied a bit more but still chosen from a limited number of options from the same suppliers.
Becuase of this it is essentially the same or very similar to a Jensen P12 series. Lack of stamps and numbering could mean that Sunn bought the standard parts and put them together themselves to save on costs but that's just conjecture, but if they were OEMed by someone else you'd expect that to be marked. They are actually very similar to RSC (the Canadian Jensen, litterally so in the beginning - they were licensed to distribute in Canada, but put the speakers together here) or even Marslands (another Canadian maker, common in Traynor and Garnet Amps) that used the same common parts. There were 2 categories of these, differentiated by magnet size - 20 watters like these and the 40-50 watters with the larger magnet (it's not the magnet that dictates the power handling, but heavier duty voicecoils are correlated with the larger magnets in this era of drive units) - so the cab is good for about 80 watts, which is about what the Sceptre puts out if running 6550s/KT88s (less if EL34)
