I use a Bausch and Lomb 5X. It closes into itself and is easy to carry in the pocket. The prices is well under ten bucks. For me it's a must have. I also have a 10X loop but I find that at that power you become to critical at what you see, unless your looking for die/strike errors and such.
I use a Globe 5x-10x. It was a cheap loupe I purchased for like $3. Works for what I need it to do (check for double dies, mint mark varities, etc). Basically the best $3 I've spent concerning this hobby.
I have used a 10x anco for along time but I just ordered a 4x from another company---I can't remember what namebrand it is but the ANA Sells it for around $17. Speedy
I have used a Bausch and Lomb 10X, and I have used others. Go to the store (if you can) and try them out. Also, the ones that the ANA sell are excellent.
For grading a 10x is too much----but if you are looking for such things as RPM or DD's then a 20x might be great---a 10x was fine for everything I needed but I wasn't much into Varieties. Speedy
Most of the time they use their eyes. Professional graders only use magnification when necessary, and then it's 5x.
One thing I've noticed, the coin shows that I attend has very dim yellow light. Even with the magnifier it doesn't give an accurate picture. Once outside it looks different. I guess I need one with a light!!
But doesn't just about every table have a swing arm lamp attached to it ? Those lamps are to be used for viewing the coins individually. In today's world there are a half dozen or more types of lightbulbs available, and each one of them can make a coin look different. When examining a coin for grading or just examination a regular 75W - 100W incandescent bulb is recommended.
There is a reason they use the yellow (regular) light, fluorescent light does not show defects to the naked eye like incandescent light does. It also makes it harder to judge the luster.
I didn't know that. I always find it difficult under the yellow light. I was thinking of getting something like the 7X eschenbach LED magnifier but seems pricey.