There is confusing ambiguity in that Wiki article, because 'wiegand cards' are antiques and not the same as 'Wiegand Protocol' that is still in widespread use, for 125 kHz or even 13.56 MHz credentials:
Essentially a wiegand card used 37 short wire segments, each tuned to read a different bit value when scanned by a reader. It is still contactless (not optical like a barcode), but it was rapidly outclassed by 125 kHz resonant-powered cards. (Which in turn have been outclassed by 13.56 MHz cards.)
The exact number of wire segments varied. In the beginning, it was only 26 (ie: 26 bit). The physical size of the card limited the tech to about 37 in widespread use, although you can find whitepapers online that describe the possibility for bigger values.