[sdiy] Synth memory chip questions

[J. Larry Hendry]

OK, I have had no luck with a Google search even finding many of these, and
zero luck finding what the variety of numbers / letters mean.  So, I am come
to my favorite place to ask the experts for some good advice.

I am looking for a 256Kx1 memory chip (it is out of a Korg DSS-1 sampling,
but otherwise analog synth).  The number I am looking for is NEC
D41256V-15.  Thanks to Google, I found a guy with some chips for sale and he
tells me the number on his chips is:  NEC D41256C-15.  The last letter C
verses V is the only difference in the number.

Anyone know or care to hazard a guess as to the difference?  Speed?
Package?

Thanks,
Larry Hendry