I actually use the Walker In-Ear (hearing aid style) Game Ear. It's of recent vintage, so modern technology. What I can say is that they really work. The sound quality is pretty good, perhaps a little bit too much treble (which most people loose first, so perhaps that is by design) and not enough bass, but other than that, good sound. Volume is easy to adjust, and can go from not even on, to way too loud. Sound is a little strange, since being behind-the-ear mounting, you get a little more sound from behind you than in front of you. Also, for whatever reason, it REALLY picks up on anything you do close by, so sniffing, or doing up a zipper, or just scratching your nose, really is hugely loud. One nice thing, is you will pick up on sounds you would not have heard otherwise, even at normal volumes. During a recent pheasant hunt, I was pointing out to my buddies where the pheasents were in the bush, as I could hear them clucking. They thought I was drinking, but sure enough the darned birds flushed each and every time. And yes, they do volume limit (not shut off) for loud gunshot type sounds, which is nice as you don't get that "I've gone deaf for a second" feeling, rather a "that was a quiet gunshot". The only downside is batteries (Type 13 hearing aid batteries) don't last long (zinc-air, once activated, will die out regardless if you use them or not), and the little foam ear plugs are sort of propriatary so you will need to buy them specifically for your unit.
My options would have been,
1. No plugs (obviously not a good choice)
2. Standard workplace safety foam earplugs (not bad, but I find they cut out way too much sound until you need them for the gun shot)
3. Non-electronic baffled earplugs, like the Sonic Valve II (for sound they work great, and actually seem to work properly during the gun blast. But the cheap retail versions are way too hard rubber, and kill my ear canals after a couple hours).
4. Electronic ear-muffs (tried them, they work, but way too bulky to walk around with all day. YMMV).
5. Electronic hearing-aid style (same as #4, but no bulky crap to deal with, and you can wear a normal hat or glasses).