I'm pretty sure it's a 1969-1970 Sunn Sorado cabinet. If it measures 40" X 24" X 15", I'd be practically positive that's what it is.
Up until 1972, Sunns only came matched with a specific cabinet, you couldn't but a head alone. You could buy an additional "extention" cabinet, but a "200S" was a head and a 2X15 D140F cab, a "100S" was a head and a D130 and a JBL LE100 compression driver, a "Sceptre" was a head and a 4X12, etc., no mix and match from the factory.
The Sorado was the 200S head, but labeled "Sorado" and paired with a circular ported 2X15 loaded with 15" "Sunn Transducer" drivers instead of the JBL's.
It was like an entry level 200S, in 1969 it listed for $670 instead of the 200S's $995.
Sunn's were never cheap; to put the pricing into perspective, a new Ford Maverick stickered for $1995 in 1969 (which is what a full Sunn 2000S rig listed for in 1969), and the US median household income was only $8389 as compared to $46326 in 2009.
Nobody that wasn't pro or very serious could really afford one, which probably explains their rarity today.
I still wonder why the cabinets are much more rare than the amps, since you couldn't buy the now much more common head without at least one cab.