Having just polished up the acrylic on the old Hamilton I recently bought, I'm much less worried about owning watches with these crystals. Sure, they scratch easy, but they also fix easy, and look great after the fact.
Worse than acrylic, for sure. Scratches almost as easily, but much harder to fix.
I ended up using Polywatch on the above Hamilton, especially after watching a few YouTube videos favourably comparing it to some alternatives, like toothpaste. Sure, it's a lot for a little, but I know it's designed for purpose, and all I need is a little anyway. Sure, I could have bought lots more of some similar product for much less per ml, but then what? At least the tiny Polywatch tube doesn't take up much space in the drawer with my cheapo Amazon repair tools etc.
It's hard to really capture the improvement with a photo, as the shine and colour of the crystal don't really get captured and the lighting is different, but here's a before and after:
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To the naked eye, the after is a massive improvement, clearer, shinier, looks like a new watch. There's still a few spots (just dots, not lines) where the damage was deeper and harder to polish out, but you can't see them unless you shine a bright light on it and catch the shadows. The best bit is the polishing highlights how mint the linen dial is, and lets it catch the light as intended...
Dang. That is stunning. It's a good thing for me that I've gone overboard on watches lately, or I'd be making an offer...
The above Hamilton from the mid-'60s is like that, and looks an awful lot like that Gruen, to the point where one was clearly 'inspired' by the other. Similar to your Benrus, they sold it as being 'dustproof', though I'm not sure quite how much dust would get through even a snap-in case back.