5BW 1926 Australia

Operator: James Graham Phillips was an active SWL prior to obtaining his licence and had his SWL cards printed for maximum effect.
He passed his amateur operator's certificate of proficiency on 31 May 1926 and the QSL postmark reveals it was posted 21 June 1926, barely 3 weeks afterwards.
His SWL cards served as QSL cards until he had his own printed.

QSL Card, Info courtesy of VK1DXA