Sequential circuits samplers

I just got a P2002/#0783 and i am wondering how i tell how much RAM is
in there. I see what looks like a RAM type expansion card.  it is
plugged into a port called expansion. It says "PC877 rev 0, Ron
Chaffee" on it. is that a ram expander? or is that just the stock RAM?
Anyone know? maybe that isnt memory? Is there any other way to tell
how much is in there? or should i just assume it has 1MB?  Thanks,

boothnavy