Heighway did not make an EM - they did a Barcardi table prior to Full throttle.
https://pinside.com/pinball/machine/bacardi-cuba-libre/gallery
The only other proto that got out was 'Circe' which later was changed to Full Throttle (that was written on WPC using a WPC boardset).
Romain in my time with Heighway showed amazing electronic knowledge - I would of worked with him longer if it wasnt for the MD!
Seriously - fair play for them saying 'LOOK - WE HAVE BUILT THESE AND THEY ALL WORK', unlike Heighway going 'We will have this ready next month - give me money NOW and you may get your machine in 2 years'.