How can I check which model of Neo Geo MVS do I have?

I am trying to buy a Neo Geo MVS PCB but the seller doesn't know if his board model is an MV-1, MV-1A, MV-1F and so on. Where should I tell him to look for this information?

The information along with pictures of each board are available on the Arcade Otaku wiki on the Beginners Guide to SNK Neo Geo MVS page. The model numbers are built up as follows;

MV - 1  F
     |  `-> Board revision number
      `-> Number of slots on the board
   

Here are pictures of each of the boards:

MV-1

MV-1A and MV-1AX

You can tell the MV-1A and MV-1AX apart by the fact that the MV-1A has a socketed BIOS chip and the MV-1AX does not (it's soldered to the board).

MV-1B

MV-1C

MV-1F

MV-1FZ

MV-2F

MV-4F

MV-2FS

MV-6F

Additionally, the MV-1A and MV-1FZ have a socketed BIOS, so the BIOS chip can be removed easily from the board. The MV1 and MV1F also have stereo sound by default (although it is possible to mod this onto other boards) so the connectors for sound will cater for this.