I have no idea what kind of recording system they had. I have a great story about the Blackhawk however that I don't mind sharing. In the early 90's I lived on Golden Gate and Divisadero streets in San Francisco. It was NOT a good neighborhood, but was affordable for a poor college student. One day I walked into this old man's furniture store on Divisadero near Fell street. This was about 4 blocks from my apartment. The store was really dirty and dank. In the middle of the longest wall there was a riser which looked like it was an old stage. There was definitely some kind of strange energy in the place. I inquired to the old guy running the shop about that old stage. I asked him what he used it for? He sat down and said "you got few minutes"? I said sure. He said that old stage has always been in my way, but I can't rip it out. I asked why? He said it still had the footprints of Miles Davis, Coltrane, Shelly Manne, Bill Evans and every other major jazz artist of the 1960's. He went on tell me that his shop was the former Blackhawk and that I was looking at the old stage. Needless to say I was blown away. Speechless I was. I just walked over to it and ran my hands over it trying to imagine all the great jazz that was played on it. If only it could speak i was thinking. I stood on it and clapped my hands really loud. There was pretty bad slap echo coming from the far walls. However those walls were bare. I am sure the acoustics of the place were different in the 1960's with the bar and wall decorations which he said were on the far wall. Anyway....sorry I can't answer your original question, there are probably few people left who can.
Mark
Mark