Name and Good Brand of the instrument jewelers put to their eye request

I was wondering what that instrument jewelers put to their eye to look at markings such as company name and number of karats on gold jewelry is called? What is a good brand to buy, too? Thank you. Rob

 

It's called a loupe.
The lens is usually 10x, and some are 20x or more.
The one shown below is a double.
I have several, and keep one in my purse.
You never know when you might need it!

 

Buy a decent one, using a cheap plastic loupe is miserable work. The best are by Zeiss, and Belomo are also good and nicely corrected although they are from Belorussia so there may be a problem getting them now. Look for glass triplets, these are corrected and give a much better viewing experience. Ones with an led light can be useful for dingy salerooms and church halls. 10x magnification is the standard, a 20x may be useful on occasion but they are more difficult to use especially if you don't have good light.

For at home use a good binocular low power microscope knocks spots off any loupe, but much bigger and a lot more expensive of course.

 

The one I've been using for 15 years (bottom)
was $1.99 with free shipping from china on feebay.
The top one was a more recent purchase to have a a spare. Up to $2.99. Both have fine optics. 20X. The newer one is less comfortable on my finger due to thinner frame.

It is ludicrous to pay for a name.

 

I have a 40x, and one of the doubles on my kitchen table. A 12x, odd number for sure, lives in my purse; I found it in my dad's miniature tools and Lord alone knows how old it is.