[Eric72]

Topps cards from ‘52 through ‘80 can vary in size without being altered.

Check the edges for even oxidation. Although not perfect, this is a good way to tell if a card has been trimmed recently.

If possible, take a look at a stack of other cards (preferably commons of relatively low value) from the set. Study them, use a loupe, get familiar with the fine details. Develop an eye for the way the edges look in their natural state. Again, this isn’t perfect. However, you’ll more easily spot trimmed cards this way.