Michael,
From V. Bobba's book on Swiss lugers on page 160, the pistol you are considering is from the M06/29 5th. variation, sub-variation A; with serial numbers around P77942 to P78258...should have black plastic grips and magazine bottom.
The Simpson LTD web site list a P781xx with an asking price of $ 2950...but in 7,65 cal.
Cannot help you with the pricing of a 9 mm variety...since they are so rare...if indeed factory installed. V. Bobba says a few were customer orders and also some W+F evaluation pieces.
Regards,
Pete... <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />