John Gartner was a fine printer and publisher, an author, a noted philatelist, and also collector of Australian banknotes and coins. He was born on 16 July 1914 and was largely self-educated, leaving school at fourteen for work following the death of his father. Gartner developed a strong interest in the history of typography and printing and was apprenticed at the Advocate where his father had been a linotype operator. Aged 17, Gartner bought a hand press and some fonts of type, and in 1937 acquired a platen press from which he set and printed his private press books, published under the imprint of The Hawthorn Press.
Gartner had a strong collection of Australian bookplates. He also looked at the work of artists overseas and commissioned personal plates. He subsequently built an international collection with preference for artists who printed from wood. His initial searches were in Belgium and Holland.(http://www3.slv.vic.gov.au/latrobejournal/issue/latrobe-84/t1-g-t7.html)
The letters J G appear on a blue hexagonal background.