From my perspective, these are Scott Tanks that someone has converted to a U.S. Divers Company manifold for doubles with a Scubapro backpack. I have a Scubapro set of double 72s that have the same band set, and I just put the same backpack on it as you show. I just got mine hydroed for the first time since 1980, but mine have the standard 3/4 inch opening as modern tanks. One thing to be aware of is some dive shops don't like dealing with 1/2 inch tapered tread valves.
My book from my library titled "
Dive, The Complete Book of Skin Diving," by Rick and Barbara Carrier, Wilfred Funk, Inc., New York, 1957 lists the Scott Hydro-Pak by Scott Aviation as having a:
"6350-B5 Cylinder and valve assembly, 48.3 cu. ft. @ 1800 p.s.i."
Your cylinders are stamped for 1800 psi, so I assume that these are the cylinders you have. They hold 48.3 cubic feet of air in each tank, for a total of 96.6 cubic feet of air for the doubles, and therefore are relatively smaller and lighter than twin 72s (see mine below). They would make a fine rig for diving, and my opinion is that you need to get them hydroed and back up and diving. If you need help with the 1/2 inch tapered threads on the valve, I've been doing that for years.
Here's a front view of my "new" twin 72s, with a similar band and backpack.
IMG_1630 by
John Ratliff, on Flickr
SeaRat