Identifying Error Coins

Great question. The answer varies, but I know that new Indian Head cent varieties will not be listed unless the difference can be seen with a 10x loupe.

I use a 10x for browsing coins, and a 60x for double checking my finds. Both loupes have built in light sources. This is nice, because I can rotate the coin or the loupe and watch the light fall across the coin from a different direction.

I used a 5x loupe and a 10x loupe interchangeably, usually a 5x loupe will be enough to see RPM or doubled dies for most of the noticeable varieties, sometime I switch over to 10x to confirm which variety for sure.

If I need to take a real close up shot, then my cheap digital microscope do a better job than my Canon PowerShot.

As pointed out, the coins you are looking to identify are "varieties" not "errors. In most cases the amount of magnification used to see the variety is in direct correlation to the value of the variety. Most of the higher valued most sought after varieties can be seen with the naked eye. While most of the more common lesser valued varieties take larger amounts of magnification to see. 10x-20x should really be the most you would want to use. I too use an AmScope for photographing purposes to really show off the affected areas.