I was an IPSC RO here in Australia and we wore the grey National RO shirt at all L3 and above matches if you were certified, it had our NROI logo on the back and a small logo on the chest, and flag and IPSC crest on sleeves. If you became IROA you then wore the referee shirt instead. The NROI shirts were part paid by your State and at Nationals some were handed out as a match shirt.