"They are copyrighted by Harry Swales Promotions. He was one of the first football agents & had Keegan on his books.
"However, apart from the Letraset Logo in the top left (front cover) everything else points towards Thomas Salter. Including their address for a competition and a free wallchart.
"There is a competition with a closing date of 30th April 1981."
(See later for the wallchart.)
We are expecting all the sets, apart from No.1, shortly; for now, here's a somewhat tatty No.6:
Picture Credit: The SPLAT Scan Archives (with thanks to Bob27indy)
© Tom Vinelott 2018