Well, the rev 1.2 also has mounting holes for Heatsinks and Waterblocks, so this is not a perfect method for detecting the revision.
As mentioned, there is a sticker under the PCI slots which will tell you which revision you have, and also, you can use CPU-Z to find out which revision of the NF2 chipset you have. If the revision is "C1" (without quotes), then you have a rev 2 motherboard.