AFAIK the 2 RAM slot board is the board used in the LC 580 and Performa 640. It has 2 slots, as well as the GIMO (I/O) ports for the DOS card connectors.

I've heard people saying they've seen the board in LC 630s as well. It typically only had 1 RAM slot and missing the DOS card connectors. I don't know if Apple ever sold the 630 with the 580/640 board, or it just got swapped out by people upgrading over time.