The standard dimensions of a T206 are 1-7/16ths by 2-5/8ths. However, the cutting process was not precise, and sizes of unaltered examples will vary. The tolerance generally accepted is +/- 1/16ths from the standard dimensions, though greater variances are not uncommon.
One of the exceptions to the above dimensions are the American Beauty back brand cards. For reasons still undetermined, cards with this back brand received an additional cut or cuts to thin the cards. This led to even greater variance in their size, with some American Beauty cards being as large as standard T206's and others almost completely absent of a left or right border.
Another exception to the standard dimensions are cards referred to as oversized or jumbo. These cards have noticeably larger-than-normal borders, with the most common being on the top or bottom. One possible explanation for these cards is they were printed on the outer edges of a sheet that was offset on the whole.