This is the first game featuring Magic Knight
Finders Keepers was originally released in January 1985, having been completed in October 1984
Mastertronic held off releasing it until the new year to give it the best chance of having a good chart position when the chart positions for the year were calculated. I can't recall my exact thoughts on that, but around November 1984 some cousins came to visit and they found a crash bug! So, I was quite pleased to get to fix that before it was released :)
I believe the overall chart position for Finders Keepers in 1985 was 5. This was obviously helped by the fact that it appeared on many platforms.
I didn't write any of the versions other than the Spectrum one, but I was quite free with passing the original source code to the conversion programmers, so the non-Spectrum Z80 versions may have some of the original source code in them.