FYI: I have a 1939 42. It was purchased on 2 Feb 2009 for $700. It is in similar condition, but has the correct grips and aftermarket magazine.
I believe your value estimate is on the high side and agree with the previous comments suggesting the fitment of original grips.
BTW, The link below shows the pin used by whoever made your grips:
http://www.themilitarycellaruk.co.uk...rw=1&sort=name