Posted By:
Richard Cline - RCLooking closely at the edges may provide better evidence to trimming or not.
The following is from the "Detecting Card Alterations & Reprints" section.
I believe this should be credited to DavidCycleback:
For the most part, Goudey cards (including the 1933 Sport Kings) were all cut the same way between 1933 and 1938, and therefore trimming detection is fairly straightforward. Originally they were likely cut with a machine that worked with a guillotine-type of effect that produces a distinctive edge. The typical Goudey has a flat edge - upon close examination, “striations” can be seen in the grain of the card (see image). A striation is a faint, diagonal “hash” mark.
For reference purposes, other cards of the era were cut a similar way, with similar effect - notably the 1932 U.S. Caramel cards and the 1934-36 Diamond Stars. Playballs, however, were cut differently, so it is important not to use these methods when examining 1939-41 Playballs.
Similar to T206s, the front of Goudey cards generally have, under magnification, a pronounced bevel. The bevel is virtually always found along the top edge, and usually along the left edge (although sometimes it can be found along the right edge). Depending on where the uncut sheet of cards was placed in the stack when cut, the bevel could be very heavy and pronounced, or less so (see image). It is essential, however, that you see some type of bevel - the absence of one is a bad sign, and, generally speaking, if there is no bevel along the top of the card, it has most likely been trimmed.
There are pictures provided in the link as well as additional examples of detecting trimming.