Full Set, 1 Owner, 3M Red 1680...Pull the Trigger?

[watchknut]

A friend called me last night in a frenzy...long story short, he ended up getting a one owner, full set, unpolished, 100% original, 3m serial MK VI dial, 1680.

I talked him into buying it at a ridiculously low price, and let him know that I would be a buyer if he ever chose to sell. Today he called and said that he may want to sell...he is not a vintage Rolex guy, likes new watches with a lot of polish!

My question is, what is a fair price for the watch in today's market, collector to collector?

I already have a 2M serial Red Sub which I love to death, but would have to sell if I got this one.

I have seen pics of the watch, and it is flawless, all original with nice bevels, slightly faded insert with dot, matching creamy patina on dial and hands, 9315 bracelet, and comes with outer box, booklets, punch papers, original receipt, and hang tags...not sure about the anchor. It is as close to perfection as I can imagine for a 1680 Red Sub.

Hopefully I get the chance to photograph it soon, and will post pics.

It will be my largest expenditure to date on a watch, and I want to make sure that I am making the right offer.