I learned this trick at a forum and was actually a bit surprised that it worked so well.
Yes, I already have bifocals and yes, I can read comfortably. In fact, I just had my eye exam yesterday and I'm good in both eyes, no prescription change needed. But:
Those are reading glasses over my bifocals and for looking at coins, that really is better than a magnifying glass. It's 3-D and you aren't looking at a tiny area. I suspect it would be just as helpful if you don't wear glasses and you wouldn't look anywhere near as strange.'
I'm 66 years old - way past worrying about what anyone else thinks, so I'll be using these at the next coin show I go to.
Of course there are times when you want to zoom in with a glass or even a microscope, but for most examinations, the reading glasses are enough and are very helpful.