Yeah - I love the basic Marsland alnico 12s for guitar (I had a pair of their deluxe ones, Lamplighter or something - sold them because they were worth some serious coin vs what I paid and I don't like what happens to the top end with metal dustcaps... and the later ceramic ones suffered in terms of quality - worse the later it got; a real shame), but I am definitely not a fan of any flavour (so far encountered) of them for Bass - very similar to those Eminence 15s that were stock in the 115RH, though they take more power (both are rather Jensen-like). I would have thought though, due to the power handling spec (I've seen 90 and 100 watts posted online in various places for the Traynor) that it can't be a Marsland in there (the ones Traynor/Garnet used were usually the 25 watt variety, with some 50 watters for the bigger amps; these were identical looking but for larger magnets). Traynor did use some "better" speakers here and there (Norelcos, RCFs, other things with cast frames) and I assumed one of those would be at play here.
Can't actually find any good info on what the driver actually is aside from the very misleading (from a PDF Yorkville history document; 1980 section ) "The TS-115 (100 Watts, 8 Ohms) was a single-fifteen cabinet added as a more compact alternative to the TS-215 for use with the TS-50B." The 215 was sealed not ported and did use a pair of (later; ceramic IIRC) Marslands (for about 100 watts handling) vs the TS-115. Ever since they made a separate website for Traynor (vs being under Yorkville) they eliminated the awesome 'vintage Traynor' info section that was so great for checking specs and config of the old gear - it even listed drivers models most of the time. There's some info on the new Traynor site, but not all the stuff that used to be over at Yorkville. A real shame - that was a resource I referenced often.
Never been a fan of any JBL 12s for guitar, though I did like the E120s I had for a bit for bass, though I only used them at low volumes before selling them off. Never used their 15s.
Anyway, it seems I'll just keep my eye out for these guys at my local gear places where I could get a good look at one - though I would totally risk it if the price is right (like the auction). If they're as large (internal volume) as it appears to me that they are, I should be able to get a driver I know I like sounding good in there and the original speaker should be worth something to help fund the replacement (even if it is a Marsland - I remember when I was buying all of them up on ebay - $10 for the 25 watters and no more than $40 for the 50 - those were good times, but no longer, the word got out).