If its a police trade in, it is unlikely to have been refinished, more likely nickel which is likely in better condition than blued.
But if it said "Fair" condition, dont expect it to be great as there are probably at least 2 maybe 3 better grades - Excellent, Very good, and Good. And there may have been an upgrade for Hand Pick.
Look at the other pistols they are advertising and compare pictures with their grading for a best guess. Based on the photo of a "Fair" 5904 (granted blue) I would consider it to be a shooter or truck gun rather than a future prized acquisition.
Assuming it goes to your FFL, you may have a choice to reject it - make sure you examine before you sign the background check - once you have done that it is hard (potentially expensive if not impossible) to return.
I once returned a 10 series revolver that was really beat and no where near matched the photo or grading. Dont remember exact details but it was either AIM or Classic as I recall - I have bought from both and I have also had good pistols from both that were as good or better than picture.
No point in fretting about it till you see it. And if it is a shooter you are looking for and you got it at a really good price, you probably got what you paid for.
Good Luck, Ed