I don't know where my text went but, I was just wondering if it's a common practice to grade dirty coins? I realize this one happens to be first in the series and of a high quality but... I kinda like my coins shiny. Feel free to criticize me.
That looks like toning from mint set cardboard or album. Some toners are nicer than others, but color (not dirt) doesn't affect the surface of the coin, a big part of what's being graded. Check out some early 50's mint sets in original cardboard; some coins are unrecognizable, some look like G-d himself went to town with a palette of pastels
1932 quarters were not sold in mint set cards from the mint. If it was put into one, it was done by someone outside the mint. The first mint set cards were issued in 1947. To answer your question, many coins are certified "dirty." The dirt is toning, and for many collectors it something they want to see unless the coin is fairly new. I do understand you concerns about this piece, however, because I don't find this toning or tarnish to be attractive. Some people like this look, but it's not something I would chase down. Plenty of "white coins" are out there and many of them have not been dipped or have been dipped in such way that it makes no difference.
As has been explained, that is toning on that coin not dirt. But to answer your question, yes, dirty coins are cleanly graded all the time. I'd say there are millions of them that have been graded. Granted, most of them are in the circulated grades, but more than a few MS coins with actual dirt on them have been graded.
