David,
Just for you I have retrieved my small single tank. It is and "Interesting one"
It is 14 inches high X 3 inches in diameter
'The marking's are as follows:
DOT 3AL 2216 237
CLIFFDIV 3 83 T A 11 (the "A" appears to be a stylized symbol for the Hydo testing facility)
The valve opening is unique! A 1/2 pipe tapered thread valve will not fit nor will a 1/2 Sportsways straight thread valve fit, but both are very close.
To make the tank usable it would be necessary to turn down a valve to fit the tanks threads
It has a VIP dated June 1984 from Underwater Habitat in Santa Ana, California- (I suspect they may be out of business)
It "appears" to be either coated or raw aluminum.
I had intended to use it as a recovery tank for spearfishing but never got around to needing it.
I do not have a clue especially at this late date what it was originally produced for or who CLIFFDIV is or was.
The tank is new never used, never in the water.
It is a very unique rare tank, so the price is $50,000.00 - or less...........
SDM