A hundred series ford, maybe more likely an 800, '01 series was a fairly popular model to have one of these on, my 850 has the 4 pt mount still on it, whereas you would set the frame into the bottom 2 arms and then tighten down down from the top, to clamp it in place, and this was part of the the Wagner loader frame, which makes it a full frame mount. An abusive operator can do some damage to a tractor like this with one of those, my loader frame was broke just after the flange connection ahead of the rear axle, and that's where the stress or fatigue point would be on that frame.
I would think it would be an inexpensive backhoe, and still a handy unit to have if it were in decent shape, there are some issues I can see from here, will mention that last. It appears that there is a hydraulic reservoir on the unit and that you would need a pto pump for the tractor, as I doubt the tractor hydraulics would be sufficient to operate this, maybe not, but it would likely be painfully slow. Someone on the forums here has one of these or similar on a hundred series, that was rebuilt, that would be the person to talk to. I would like to see a shot of the frame, I can't see how it would connect, per the above, but there was a Dearborn, factory made 4 pt full frame mount for hundred series Ford tractors, I have a photo of one that was for sale years back somewhere in my file directory, would have to find it etc.
If the pins and bushings are tight, and not sloppy, that would be a decent find, however, and I say it with a degree of respect, the owner was really foolish to store it like that. The swing cylinders appear to be heavily rusted, you can see the boom and stick cylinders have a nice "hue" of rust on them too. The hoses, being weathered could be prone to burst, well I say that but I have some really old and weathered hoses on my Wagner loader, its hard to believe none have burst in the 11 years I've owned it, and I have used it extensively for clearing, snow removal etc, but the pump may be worn or just not enough pressure, it is slow moving, but can lift more weight then should be placed on the front end of a general purpose tractor like an 850. On that note, I would have to believe you need a loader on the tractor to balance things out.
One thing is for sure, I'd want it for scrap price if the owner is not stubborn you have at least 2 cylinders that will need to be re-chromed, they may be pitted beyond repair, hard to say. The others you may be able to clean up, but they will rust very easily again, well unless the are retracted. Use it as is, the packings in the cylinders will likely get damaged, and that will make them leak. I can see some money being spent at the local hydraulic shop, and as a matter of a fact, thats where I would drop the thing off first LOL !
Given what it is, though and your interest, it may require more that it is worth, but it is of the 50's era or so, and a collector may want it or you may want a period tractor, likely a Ford, these were common on 820, 821, and maybe the same for 620, 621, as those were bare basic models, that I believe the 3 pt may have been deleted, but you still need the pto, I don't believe you could plumb this off the 2 spool loader valve, and use the reservoir from loader, and front mount pump.
Its an interesting piece and makes for a nice discussion, hopefully someone with more details can help, if were me, given my tractor is set up for one, and also been hammered by one, I'd consider it if the owner would negotiate down, shameful he left the cylinders extended like that, would be worth the money he is asking, but not so much now in my opinion.
You may find an old manual for it on ebay, Sherman Power Digger, the other parts; pins, bushings and hydraulics are not complicated and could be sourced in a variety of ways, steel or machine shop, and your local hydraulic shop. Likely a 4 stick operated hoe, that will take some skill to master, but still handy to have one regardless.
Best of luck with it !