OK Buddy, here ya go. There was a cabinet that was in production from at least 1970 until 1975 as it appears in the catalogs for both of those years. The 1975 catalog shows it with a model number of 612SP.....Description....V-type front loading Horn; Six 12" Sunn128G Speakers.....Impedence: 6 ohms; Power capacity 300Watts RMS..Size 42" high, 24" wide and 15" deep. The weight is 105 pounds. I may have a 1975 price for you if I look long enough.
The LIST PRICE of this behemoth in 1970 INCLUDED the ever popular Sunn 1200S head (yes folks-I actually own one of these heads) which put out a massive 150 watts. At THAT time (1970) the cabinet could be ordered with either Vega speakers or JBL D123F speakers. Sunn dropped their affiliation with JBL shortly after that.
What's it worth? Whatever anyone will pay for it. I know, that sounds rather vague but I've found 2000S cabinets WITH JBL speakers ranging in price from $150 to $600. You're correct in assuming that there aren't many of them around. Most of the really big Sunn cabinets ended up getting trashed from being moved or were chopped up in the late 70's and early 80's when men became panty wastes and chopped them down to make them easier to transport. If I had to put a value on it I'd need to know what it had for speakers. Off the top of my head, the cabinet is probably in the $200-$250 range unless it has JBL's that are in good condition. If I had it, I'd keep it.
Related--SUNN had 6x10 cabinets which used the same box and they recessed the speakers back a bit more. Also available: 3x12 cabinets that you could use side by side. Each of those were 6 ohms as well, however.
Hope this helps.
Bass-ically Yours,
Rich Briere
www.richbriere.com
