A very popular and ground breaking game on the Spectrum, was in fact also planned for the Commodore 64 back in 1987.
Sandy White, creator of Ant Attack and Zombie Zombie, set to work on creating one of the most ground breaking 8-bit games of all time, up in the ranks of The Sentinel.
The ZX Spectrum version was completed and released, but the C64 conversion never surfaced or was never heard of. It seems the Amstrad CPC version also befell a similar fate. There was a mention in German Happy Computer magazine (issue 02/1986) with the C64 format listed, possibly taken from the adverts at the time.
Checking the advert (which you can see on the scans tab below), I Of The Mask was indeed intended for release on the Commodore 64, though all screenshots are that of the Spectrum version. It is very likely that any conversion was too slow.
Sandy White was asked about the C64 conversion, but no response was given, though rumours that it was Sandy White coding the conversion are confirmed to be false, with him only coding on the ZX Spectrum.
This confirmation came finally in 2009 when Richard Hewison got confirmation that there was indeed a C64 conversion underway by Paul Fik, who also converted Sandy White’s Ant Attack to the C64.
Attempts were made to try and locate Paul, but we’ve had no joy as of yet. We did find a Paul Fik from Plymouth, but who had passed away back in 2004, and we feel might be the same person unfortunately. Hopefully we are wrong and we can track down Paul some day.
Contributions: Dumbflag, http://www.Zzap64.co.uk, Martin Pugh, Richard Hewison, Wilfred Bos, Fabrizio Bartoloni, Mark Jones