I think it refers to the maximum clock frequency of the part. -8 means an 8 MHz speed limit, 10 means you can go up to 10 MHz. Either should work fine in a Plus.
The "p" is for Plastic dual in-line package. (Other manufacturers say that differently, but that's what it means for a 68000.)
Shame about the broken pin, but don't throw away the chip, I say: keep it around for when your soldering skills improve (or dremelling skills if you broke it off right at the edge of the package!) and you can bodge on a replacement leg.