Info about the 212 and the 512 series preamps is not hard to come by. However, the 312 is more elusive. Were they manufactured for use in any of the 1970's consoles? If so, was there some sort of faceplate? Does anyone have pictures? I've just purchased one of the vintage 312 cards and I'm looking for another in order to put together a 2 channel unit so I'd like to get as much background as possible. I'm considering Brent Avrill's people for racking them up. Suggestions, recomendations?