Clasisfication of class A, B, C, D ... MFH and apartments?

[Jerry N.]

I think I use to know what the classification of class A, B and C apartments meant but recently that knowledge has been challenged so here is my question.
Could this very from market to market or even investor to investor?
From what I have seen these terms have not been used uniformly by everyone.
As an example all my MFH are in the cities not towns.
Up to now I have classified these as B and C class. My C class is right in the city clean older building, safe street but areas around are mixed, there are some streets or buildings that I would rather not touch. My B class is still in city but more like a townhouse between 2 family and single family homes very quiet and safe neighborhood.
Recently I was investigating potential purchase that was presented to me as C class, however I was shocked with the condition or even amenities of that property. In my judgment this would have been E or F class property
Is there some sort of generic rule to classified property by location, price, condition or any other qualities?

Thank you.