Nir:
XEM65OS.256 -o.s. that found in a XEM65. this computer appeard to be a 65XE
but with BASIC ROM removed and a larger EPROM used for the o.s. (27256).
this appeared to have been at one time used as a prototype for the XEGS
development, maybe?

Freddy:
Very strange. If this is really from the XEM65, it's exactly the
same as the XE Game System ROM. First 8k Missile Command, second 8k BASIC
and last 16k XL/XE rev.4 OS! So, BASIC is not removed and the OS is not
larger! It's just everything in one chip, just like the XEGS!)