Well the tanks could be worth $50 scrap. The Mark V looks okay but it appears to be an early two port. Photo was not very clear.
When venturing into the collector or vintage world the condition of the equipment and the item itself are everything. If you only paid 50 dollars for it I would use the regulators as a learning tool. Take them apart, see how they work, learn to begin to work on your own gear.
The tanks are essentially worthless, seriously, except for scrap.
Regulators:
USD/AL Conshelf
SP 109/108 with Mk V/X etc.
Anything USD Aqua Master/Mistral or Voit double hose (you can at least sell it for dollars or trade)
Essentially anything USD/AL and Scubapro can be fixed and updated
BCs:
Do not buy used BCs
Wetsuits:
Do not buy used wetsuits unless you like swimming in other peoples urine
SPGs:
If it is SP brass or any brass and glass construction and works, good, if not, do not
Fins:
If they are Jets, maybe, if not, then do not
Masks:
Just go get yourself a mask that fits, SP, AL, Mares all have a variety of good masks, the Atomic Frameless is to die for and you might when you see the price.
Knives:
Yeah, if it is a Buck diving knife, a USD SeaHawk or a Tekna Dagger or SP Dagger, yes, if it is butter knife or scissors, I am sure your wife already has some you can borrow.
Old depth gauges, watches, instruments are fun to collect but, frankly, for diving, get a cheap computer with Nitrox capability.
The Dacor thing, some people seem to like the stuff, I am not one of them. Dacor did have a few nice horse collar BCs back in the day but for the most part, if it is Dacor, run, run fast, there is something better in the next CL posting I am sure.
Mares, then and now, I love their fins, masks, their regs, nah, anything labeled a HUB or even resembling a HUB, run even faster, if you want to get laughed at, then go right ahead. They make great gag gifts or Halloween costumes.
TUSA, gag, gag, puke, vomit.
N