Will,
Last Vickers I saw that was for sale in the past few months was with FGS, Inc. out of Ohio. I think their asking price was $ 3750...granted probably a bit high as they are a retail/dealer.
I think theirs was in a bit nicer in condition that yours, but yours is still very nice.
My guess on your Luger...$ 3200 or so...
Your gun seems to have some active spots of rust & pitting. Some cleaning and lubrication would be advisable so it does not get any worse.
BTW...here is a snapshot of my Dutch KOL from the 1928 contract...same/similar unit plate as yours...
I bought this one from Member Ron Wood a few years back...it has ties to my father...having served in this same unit...when he was a young fellow in Indonesia...