How to tell what os is installed

I found a guy who might sell me his mpc1000 for $600. So far I know its the older blue one, and it doesn't have the pad upgrade. I asked the guy if it had the jjos installed, and he said he didn't know. He is the second owner, and he said he doesn't really know how to use it. I assume the os # flashes on the screen at startup. How can I tell a guy who knows nothing about the machine to look up the os for me? Also, is $600 a bit steep for a pre-pad upgrade blue mpc?

Hit MODE and OTHER and it will tell you what version you have. I have seen people get the og blue ones for less than $500. Buy it as cheap as possible and fix it yourself, right Nym??

Word, I just copped one on ebay for 420$ shipped.

The deals can be had, just be patient...and have the money ready, but I see them go for 500$ all day long on ebay...the one I'm getting is supposed to be in excellent working order with almost no play time on it.