Ebay item

Surely the 1918 date is incorrect as they were not sold in the UK until 1920 and I thought the G&R motorcycles were later.
More importantly, did G&R make their own engines or were they supplied by Selsden who made them for Sopwith?  A good indication would be whether they used metric or imperial threads.
My pre-war Morris cars were entirely built in England but the engines have metric threads with imperial heads as Morris took over the Hotchkis engine factory in 1924 and retained the threads until they were replaced by Austin engines after WWII.

Gnome & Rhône a livré ses premières ABC à partir de 1920. La moto en annonce ne me semble pas être une ABC Gnome & Rhône malgré le logo sur le réservoir. Pour moi c'est une ABC anglaise. Les ABC françaises sont toutes au pas métrique.

Merci, les machines anglaises Sowpith ont été retardées à cause de la pandémie de grippe espagnole autant que de la grève des fondateurs de 1919. Les Gnome et Rhone ont clairement été entièrement fabriqués en France.

British manufacture makes sense as I found it difficult to understand why a French machine would be exported to New Zealand.

Looks like New Zealanders are falling out of love with their ABC's:
https://www.facebook.com/groups/2056968301023163/permalink/5919493308103957/?sale_post_id=5919493308103957

I think that it is more likely that the generation that love them is dying out. 
I know the feeling anyone want to buy the only sports car that Morris ever made - a Ten Six Special four seater with its 1372 six cylinder engine?