I have 31 marten to sell this Saturday in Montana. I have one which is ragged and flea bitten and looks terrible the rest are great. Do I put it with the rest or sell it separately?
Also is there any advantage to sorting my marten by size into different lots or will thy all get mixed up anyway?
My goal is maximum total price, I don’t care about my average particularly. Thanks!

I don't trap marten but I'd sort them out even if you did it after you get to Livingston .

The poor fured marten will bring down you're average , I'd ask Guy or Bob when you get there maybe they can give you better advice .
The advice I'll give you now is I'd post this to the Montana Trappers Chat you'd have a better chance of getting quicker response than here on a strict trapping only chat .

Maximum total price = your average.

A bad pelt is gonna bring down your average whether it’s in a lot of better stuff or by itself.

If it’s that bad, maybe keep it. Tan it or something.

Personally, I don’t pull one or two bad pelts out of a larger lot (except maybe cats).

Use the good fur to move the bad fur.

The bad fur by itself may not sell at all, than your stuck with it anyway.

I figure there are always crafters that may want to work with a less expensive or damaged pelt, and separate them out for those people.

I’ll ask when I get there and likely sell it separately. Thank you!

Depends on what buyers are there, which way will be better. As Dean says, if there are crafters there they may be willing to pay a little more for it than a buyer who is looking for good grade marten. On the other hand, if there are several buyers there that want your good marten, even if they don't want your poor one, they will bump their bid on the whole lot however much they figure they can get out of the poor one (they will know buyers they can dump it to if they don't want it) to make sure they get your good ones. But if you seperate it out, they won't even bid on it if they don't want it themselves. On the third hand, if there is only a buyer or so there looking for good marten, they may bid the same total for the whole lot whether that one is in there or not (which means you gave it away, if you lotted it with your good ones) while the crafter looking for a deal on a couple cheap furs to work with won't bid on a large lot of mostly nice skins.

If you don't know what buyers are there and what they are looking for, I'd go with whatever the guys running the sale advise, otherwise it will be a guessing game for you.