When I got my first one, away back in the '70s, it was the 'thing'. I used it exclusively on a .22LR and while it never pretended to be a target scope, it accounted for a good few bunnies. And a few running ones too, IIRC.
It had the radioactive green dot which appeared when there was insufficient light for the red one to show and I remember there was a warning that the radioactivity would have decayed by some time around 1995 - 2010 resulting in the loss of green illumination - can't quite remember the date but do remember thinking that it was so far in the future, it didn't matter!!
I mounted one of them on my 223 just after I got it about 10 years ago after having missed opportunities on hill foxes that appeared 20-30 yds in front of me. By the time I'd acquired them in my 6.5-20 scope on 6.5 mag, they had scarpered. Worked fine for close up work ie up to about 30 yds.