How Do You See Hairline Scratches In Dim Light, Like At A CO

I purchased a magnifier from wizardcoinsupply that has a built in LED light. You can find one on ebay as well.

The best way of detecting hairlines on a coin is to tilt it at several different angles under a point source of light, a): without magnification, and b): with magnification.

At a coin show, a table lamp is probably the best you can hope for, and in most cases, is OK for the purpose.

I understand your problem. With older proofs, such as a 1937 British proof five pound gold coin, there is a difference of hundreds of dollars in value beteeen an FDC (Fleur de Coin: from French Flower of the Coin) and a 'nearly FDC' example. FDC coins are absolutely perfect in every way, and require careful storage.

BTW, I have such a coin, and that is why I have used it as an example. My coin is stored in an acrylic screw capsule.

Modern proof coins are often marketed in permanently sealed capsules ex mint.

Any reputable dealer is going to have adequate lighting at his/her table.

I refuse to buy something over 20$ from a dealers table with no lights. I assume the there trying to hide something or they were just to lazy in the first place to invest in something to help there sales.

For general grading, 10x. Higher magnification, including stereo microscopes for detail checking.