[RShaw]

I estimate an authentic matching mag would add about 30% to the value of an all numbers matching P08 in good overall condition: at least 80% original finish, minimal pitting, holster wear only, good bore, grips undamaged.
2 matching mags? perhaps double the price?

Depends of course on what the collector/buyer is willing to pay.

Perhaps go through buyers' sites and compare two firearms as close in condition as possible with the same manufacturer and close to the same date- one with matching mag, one without. Would be an interesting excercise. Might do that myself come to think of it.

A quote from the Luger Catalogue:
In the rare case when one finds a Luger with a
proper matching serial numbered magazine, the value
goes up from 25 percent to 50 percent. In the extremely
rare case when one finds a Luger with BOTH proper
matching serial numbered magazines, the value goes up
as much as double.