when you send furs to auction they are graded on size, color, fur thinkness, handed correctly etc
every species have different grades and traits that make them more desirable then others
the furs are grouped together by these common traits by the graders and then sold all together as a lot
top lot means for that species they are the most desirable graded furs that sell for the most money
example would be a female xl size uniform dark color marten caught in prime fur trapping season could make it into the top lot because that is the most desirable type of martin fur by fur buyers
here is some handling info from nafa
http://www.nafa.ca/wp-content/upload...al_2012-02.pdf
here is how coyote are graded, the ones with pure white bellies and pale backs are the most desirable
http://www.nafa.ca/wp-content/upload...009_Coyote.pdf