I'd say that it's a Sunn 4 x 15",but how about that Peavey Super Festival Series head,you don't see a lot of those around these days.If I remember right,they made 2 models,a 200 watt and a 400 watt,all tube,6550's/KT88's for outputs,early 70's I think.Those amps sounded pretty good,the idea was an amp that could handle guit./bass/or keys,the cabs had 4 x 12" and a large radial horn,ouch !!