The C, M and U refer to:
C=Coated
U= Uncoated
M=Matte
V=Video
More here:
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Pantone has also renamed the colors in the tables. Pantone 485 is still the same red you’ve always known, but older versions of the various tables used in typical publishing programs like Quark, Illustrator and PhotoShop may have added different tags to the color. You are no doubt familiar with the fact that Pantone 485 has for many years had a coated and uncoated version, logically called Pantone 485C and Pantone 485U. But, you may encounter Pantone 485CV, CVC or CVU in the tables of older versions of the publishing programs. CVC and CVU were suffixes for "Computer Video Coated" and "Computer Video Uncoated" to signify that this was a video simulation of a Pantone Color. This suffix would sometimes be truncated by the publisher, which is why it would sometimes be represented as 485 CVC in one software program and 485 CV in another.
Once again, what Pantone attempted to do is make things simpler and more logical. The printed color guides and the color in the digital tables now match. The color tables in the latest versions of Quark, Illustrator and PhotoShop reflect this. Because the new guides are printed on Coated, Uncoated and Matte papers, the codes are either C or U or M. In the short term, of course, this adds to the number of possible codes since many programs which have not yet been updated are still in wide use.</div></div>
Hope this helps!