I would vote for authentic...
Here are a couple of others for sale on the Internet.
I have one as well with a 4-digit luger gun number stamped on the front of the holster.
http://www.collector-arms.de/produkt_images/800260.JPG
On Joe Salter's site, click on his "luger" section and you will see another with lots of good photos down the page a bit. You can compare those photos with your holster :
http://www.joesalter.com/