A 45 Luger Carbine, wow!?!? I know that someone, in the '90s I think, but my mind is a little fuzzy on the subject (and others besides), had access to SN 2 and took measurements. He made something like 100 reproductions, and they cost about $11,000. A friend, a real Luger collector has one, and I've examined it; a great job. I didn't know he made carbines though.
I've head both SN 3 and SN 6 for this pistol. SN 3 sounds more likely. From the pictures it differes from SN 2 in the trigger. SN 2 has an almost straight trigger with a hook at the bottom, while this is semicircular like other Luger triggers; odd. Wonder what other differences there are, and wonder how the Norton museum reacts to requests to examine the pistol. Also wonder if it is marked with Georg Luger's initials?