That would be an import mark that was added sometime after the gun left the factory. There was no need to put an import mark on a military accepted firearm for use in Germany itself.
It's very likely that you've purchased a reworked Russian Capture or DDR police pistol. These were refurbished in the communist block after the war, and saw service for several years.
If they were made surplus and imported into the USA sometime after 1968, they would be required to have an import mark added. Thousands were brought into the USA this way.
These generally lose their collector value, but make great shooting Lugers in many cases.
As you wait for your pistol to arrive, download a copy of the forum's FAQ PDF document. You'll find it a useful reference, with a remarkable level of detail collected by forum members over the decades.
If the details are still on gunbroker, why not post the link?
Here's where you'll find the FAQ, and welcome to the forum.
http://forum.lugerforum.com/showthread.php?t=13121
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Igitur si vis pacem, para bellum -
- Therefore if you want peace, prepare for war.