Here's a scan of a stripped MIFARE Ultralight smart card. Most of the wiring is the antenna which effectively consists of a single spiral track. The outer spiral turn clearly is a bit wider than the other turns while all the other turns have equal widths.
Why is the outer turn wider than the others?
Probably for mechanical reasons. It is the feature nearest the edge, so it is more likely to get bent or cut. Making it wider makes it stronger so it is less likely to get damaged.
My Guess would be it has to do with a tuning of the WI-FI system or the proximity sensors used to read it, might even be a way of tuning a spcific card to a specific user maybe some Proprietary signal characteristic for the Mfger to say their product gets better signal strength to improve security scanning device response of it.. Definitely a Mfger specific reason for increasing amount of conductive material in this specific location.. It would be interesting to test this signal return vs other similar style antennae to find out how this "turn" on the transformer impacts the overall SNR of this specific design. The materials concept may pan out but, remembering that these things are usually glued to something, the durability factor may not be as important to the Mfger. as something else..Considering the cost even in an economy of scale could be noticeable due to Mfging sequence changes, There is an important reason for the engineering design used here..
