Hi
I believe the first machines to have a nudge feature were made by Carfield Engeneers in Leeds (still going but now known as Dransfield) however I cannot remember the names of any of these machines now, I remember playing one on 2p play in the local arcades in the late 70s, essentially all the other manufactures had to pay Carfield a licence fee to use there Nudge feature, if you look on the reel glasses of nudge gambler and also on Nudges unlimited you will see Licenced under Carfield nudge patent no (the patent no),
If you want to read more scroll down this page on Dransfields current web site for the section the history of the nudge
https://www.dransfields.com/about/the-dransfields-story/