> Where do I find the eprom version of the D-50?

All you want to know about your D50 ...

if you HOLD keys SHIFT + INCREMENT
or SHIFT + DECREMENT
or SHIFT + WRITE
or SHIFT + DATA-Transfer.
WHILE you POWER-UP the machine it will show more info in the display.
and you can test all buttons, controlers, ...

regards,
~/Eric.