Posted By:
JimBSean,
This is not an exhaustive list, but some telltale signs are:
1. swurving uneven cuts.
2. bat ears on the corners
3. a tilt cut on one side that is not identical on the other (this is not necessarily a sign on 19th century items).
4. obviously uneven wear on corners (e.g. 2 vg corners and 2 nm corners)
5. undersized
6. if it is unslabbed look at the edges. If the toning on the edges is uneven, it is suspect, especially if the lighter edge has other indicators. If all the edges have been exposed for 95 years, they should have roughly even toning. If one is particularly light, it may not have been exposed to the elements for as long (i.e. was trimmed).
7. irregularities in the edges.
8. card is in a PRO holder. 
I'm sure others will have more to add, but this is a starter.
JimB