Special prefix for Switzerland (HB)….

The Swiss national radio society Union Schweizerischer Kurzwellen
Amateure
 (USKA) will celebrate its 90th anniversary in 2019.

Throughout the whole year, HB9-stations may use the prefix HB90,
together with their suffix; and HB3-stations likewise the prefix
HB30.

https://www.uska.ch/

DXNL