Just because a grandfather's Luger, that was captured during WW2 was stored in that holster for 40 years, doesn't mean that the holster is a genuine German Luger holster... All of the stamps are wrong... you can buy stamps to say anything you want and put their mark on anything you want, that doesn't make them genuine.
To quote a statement from a recent election with a poor outcome"
"You can put lipstick on a pig, and it is still a pig"
Get your money back and use it for a downpayment on the Luger... Why do you think they sold the holster separately?