[Crimediver]

The two in the picture are Dacor J-valves. They are built to be bulletproof and are solid brass. There is a HP port on those valves that a SPG hose can be screwed into for monitoring air supply. They were popular back in the day when many regs had no HP port. I use them in vintage diving with a Voit double hose reg.

You will need to see if the valve threads are 3/4" o-ring sealed thread or 1/2" tapered pipe threads. The double manifold will be easier to use if it is 3/4" or you will need to score some old steel 72 tanks with a 1/2" neck.
A vintage diver would use them but most divers or LDS will tell you you need a manifold with an isolation valve, etc. If they are 1/2" you will need steel 72 which would require you to find a set of bands to fit it. The diameter would be 6.9 inches. The tanks will also be lower pressure tanks like 2250 psi or so. If you are interested in setting up doubles PM me and I can steer you to some vintage dive suppliers than can assist you. The j-valves had a rod attached to the lever that a diver would pull to activate the reserve.
FWIW the j-valve is not obsolete and is currently used by the US Navy and may be mandated by OSHA in certain diving applications. It is still currently manufactured and is a LOT more expensive than a K-valve.