I'm guestimating 10-20% magnification. The viewing angle isn't cut down much, but it's a little distorted around the edges at any angle I think.
I did a little Google image searching and found
this one that's almost identical but has a custom base. Mine has a little screw at the bottom too, and I was wondering what it was for.
I was going to say solid plastic, but this site claims it's blue perspex filled with linseed oil. On the other hand this one is 22" in diameter (that's insane!) and mine's only 12".
A 7" Motorola just sold today on eBay that had a magnifier with two brass rods attached right to the top of the wood cabinet kinda like you described with pipe fittings.
Here's a
pilot magnifier attached to the front.
No way I'm drilling holes into my Emerson
I think I'll try making a little custom stand like in that link.