Here is a bit of info. from Sam Costanzo's book on Luger proofmarks; from page 234.
Do not know if this theory is dated or still valid. Will wait for the experts to reply...
My luger-buddy, Doc, has borrowed my John Walter's book, The Luger Book, so I cannot look up what Walter might have written about these guns...
Regards,
Pete... <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />