Hi there, here is the antenna pcb file and you can use the eagle to open and measure the size. thanks.
<LINK_TEXT text=“https://github.com/SeeedDocument/Xadow_ … ntanna.zip”>https://github.com/SeeedDocument/Xadow_NFC/blob/master/resources/Xadow_NFC_Antanna.zip</LINK_TEXT>
Seeed techsupport team
Bill