It has been shot. If you shot 50 or 500 if you take care of it then it is worth about the same. Until you get to 5,000 it will be worth about the same.
They are more valuable than a new MKIII but in the end they made a lot of them. Condition is everything but unless it has the pouch, original mags, etc... it is not worth more than $1000 - $1200 give or take to the right buyer.
If it were mine I would shoot it and take good care of it. Let your heirs worry about what it is worth as a collectible.