@ Fraser - There use to be a MK2.5 game called Supebucks and that had a x2, x5, x10 gamble feature afaik.
This is quite interesting but i have actually seen several games with animations running on MK2.5 - i saw a black panther machine a while back which had animations (unlike 2.5 games) running on a MK2.5 i think (but it actually looked like a MKV machine layout) - i'm pretty sure it was running on a 2.5 machine because there were a few things such as not being able to spin a new game without the music finishing and the beep sound at the commencement of each spin...