The birds were trapped and flagged by Jonathan Martinez and Professor Fasheng Zou at Xitou beach, Guandong Province, China. The flags are on the left leg - the white flag is plain and triangular; the yellow flag is square-ended and engraved with 2 numbers.
If you are lucky enough to see one, please send the details - number, location with Google Earth ref, date - Jonathan at jonathmartinezATgmailDOTcom.
There's a very nice summary of the Swinhoe's Plover story to-date on Terry Townshend's 'mouthwateringly good' blog, here.
Photos courtesy of Jonathan Martinez.