Lugers were always recognized as well made premium firearms.
There were several mail order companies on the East and West coasts and in Chicago that sold imported Lugers.
If there is no "Germany" or "Made in Germany" stamp anywhere on the gun, it was probably purchased outside the USA. I know that Lugers were brought into Mexico. Perhaps this came up from there.
The website "The land of Borschardt" has scans of several of these catalog pages.
http://www.landofborchardt.com/
Whether you keep or sell your gun, I'll warn you that Lugers are addictive!
Marc