Thank you for the report.
We do have ringed a Pacific Golden Plover with flag H4 in 2021, but it is a 1st-year bird, thus won't have breeding plumage at the moment.
I think this is most likely C4, which has been reported recently in full breeding plumage.
C4 was ringed on 30-Dec-2019.
Katherine
Waterbirds Ringing Group