measuring a card to check if altered

[Oscar_Stanage]

Hi,
I am looking at a 1966 card that I am checking if it is trimmed. I have read articles on how to check, but since I have never held a real-life altered card I cannot really tell. All 4 edges feel the same to me - none feel "smoother" than any other. However, there is a faint 'flared' corner and the top edge has parts that might be described as 'crimped'. The picture portion of the card is tilted a bit within the border and it appears that the centering is not consistent from top to bottom - top is 50/50, but scales down to 80/20 toward the bottom of the card. This might be just be a tilted picture, or the widths of the card might be different...

The standard size for 1966 Topps is 2.5 x 3.5. I measured it across all sides (at different places), and it seems to match those dimensions at all points on the card. How fine does the measurement have to be? my crude measuring is not likely going to pick up 1/16 or smaller... Is it really possible to judge an altered card by eye and a ruler?

I can try to post a picture of the card if that will be useful and you all can provide an opinion...