Actually, it's 1.86/SSD is the rev B... 1.86/120 MOST LIKELY rev C. 2.13/SSD definitely rev C. If it has 80GB or 64GB DEFINITELY REV A! If it has 120 or 128 GB, it's most likely a rev B... refurbished now.
By looking at them, if it looks similar size to two USB ports, it's a rev A. If it has one port half the size of USB, that's a mini display port and means rev B or C. Of course, if it's turned on, go to Apple symbol, about this Mac to check version and info.
Also, if it has an Nvidia 9400m, it's a rev B/C.
If someone is selling a "supposed" rev B, that has a 1.8 GHz, check more, as the original (rev A) had 1.6 or 1.8. The rev B had 1.6 or 1.86 GHz. The rev C has 1.86 and 2.13 GHz.
Finally, my suggestion, is absolutely positively buy a rev B or C. And, you get about five times the Mac with rev B or C and SSD over HDD. It is night and day difference with SSD. And, the rev A CAN BE a NIGHTMARE for SOME (definitely me). I have owned all three versions. I would say, no matter what, buy a rev B 1.86/SSD refurbished for $1449 over any other refurbished OR DO NOT BUY. If you cannot afford the SSD, wait until you can. It will make your experience so much more fun and exciting!
Good luck.
Cheers...