Ron, not to doubt you, but the one posted on Jan's forum, is this one a year ago (or so). I have seen this brought up before, there was an interesting posting by Ted Green 3 or 4 years ago, for an armorer marking, and a couple of others.
http://luger.gunboards.com/topic.asp?TOPIC_ID=8493
I am unsure if 3 to 4 engravings equals "common"....