Wow. You don't see these very often.
http://www.ebay.com/itm/MAXMACHINE-with-MINI-BASIC1-cartridge-Commodore-C64-SUPER-RARE-/112002879196?&_trksid=p2056016.m2516.l5255
According to the screen image, it only has 518 bytes of free RAM. :)
George