Majic has nailed it.
On the whole, the quality of Hamden High Standards was higher than that of East Hartford models; unfortunately, that doesn't tell you much about an individual gun. Some Hamden guns were dogs, and some East Hartford guns were as good as the older Hamden models.
When you look at any military-frame High Standard, the first thing you have to do is remove the slide and slide release lever, taking great care not to lose the microscopic spring that powers the lever. You'll see a cut in the right side of the frame to accommodate the slide release lever.
This is the weak point.
This is where High Standard frames crack if the gun has been fed anything but standard velocity ammunition. The frames were never heat-treated. The paper work that accompanied the guns stated they were intended for standard velocity ammunition only. Cracking has occurred after a few hundred rounds' worth of high velocity .22 long rifle ammunition.
If you see a crack or anything that looks like it even might be a crack, offer the seller $50 to $100 for the gun as a parts source, but not a penny more. If the frame looks as though it even might have been welded in that area, offer the seller $50 to $100 for the gun as a parts source, but not a penny more. People claim to have rewelded High Standard frames. People who really know what's what with these odd, but wonderful pistols take a dim view of such claims.
The slide and frame serial numbers need to match. Identical-looking slides often don't work right, even though they're in the same serial number range.
If the sear adjustment screw at the back of the frame doesn't actually adjust the sear to alter the trigger let off weight, you'll likely have major reliability problems down the road. If the magazine doesn't drop smoothly and easily out of the grip frame, it may well be an indicator of dimensional problems, which may be inconsequential or serious. If the magazine wasn't actually made by High Standard of Connecticut, it's most probably not going to work. If you can wiggle the bridged rear sight, you can be sure it's been taken apart and reassembled, and there's a good chance it won't work right. The bridge works very well, and the sight is a joy to behold—but none of it was ever designed to be worked on by anyone other than experienced High Standard employees. Check the breech of the barrel for a.) peening from the hammer, and b.) supposedly repaired peening. High Standards were never meant to be dry-fired.
I have three East Hartford High Standards. Two are truly excellent match pistols, and the third would be a pretty good shooter, but it requires more pampering than I'm willing to give it, so it's a safe queen. I keep flirting with the idea of buying a 107 or MS series Hamden gun, but am afraid of ending up with finding one that looks good on the internet, but turns out to have a cracked frame.
Best of luck, eh?