I have two 10x loupes that I use. One is a B&L Hastings Triplet
which I believe is probably the standard of the industry. The other is
a Zeiss with plastic case. Both are in the 50-dollar range if I’m not
mistaken. I can’t tell any difference between the two as far as
quality goes. My advise, though, is to not waste your money on a cheap
loupe. When it comes to optics, you definitely get what you pay for.
The better loupes will be sharp from edge to edge as opposed to sharp
in the middle and blurry as you go away from center.