obscure vendor selling industrial 12v batteries

Hi

Shotgun theory question. A bloke in my area is selling a very cool battery - have done the research, rated at 70ah at the C/10 rate, a sealed pure lead-tin battery, will deliver 400 cycles at 100% DOD C/5 rate. So the obsessive types may guess it is a Genesis battery. So he is selling them one by one "still in boxes" - i said "so how come you are selling industrial deep cycle batteries ?" he said he picked them up at an auction of a disposal store's liquidated stock. He is selling them very cheap. Am just wondering what sort of disposal store sells deep cycle batteries or is that cr#p. And is there such a thing as dud batteries being sold en masse and working there way into the dodgy outer suburub importer vendor market.

Naturally the safe would say don't risk it, but gee whiz $99 for a sealed pure lead-tin 70a/h @ C/10 sounds soooo cheap and is apparently still in a box - with lots of others still in a box apparently. So - bargain ? or will he not be there in a couple weeks when i notice this battery can only be charged to 80% and starts dropping its charge from day one (unlike my optima yellow to which takes about a month to drop 0.01v).