I have recently found three prototype/demo Voltmace cartridges of:
"fruit machine" which is Casino, no.31 on the Interton.  Two of these.
"space" which is Super Invaders, no.33 on the Interton.  Two of these.
"spider" which is Spiders Web, no.37 on the Interton.  Only one.
I know none of these got official releases on the Videomaster/Voltmace system.  The lot also came with two demo only not for resale "invaders" and "star war", which are the released versions of Invaders and Space Battle.  Also two early demo Videomaster cartridges for "Boxing" and "Space Battle".  
And my prized possession, which I've had since 2015, is a Radofin protype cartridge of "Chess II" for the 1292/1392 system which was proepared for the CES 1981/82?  This never had an official release on any other system apart from the Interton, same as Casino and Super Invaders.
