I would not use the word "rare" with a luger that comprised a near complete block of 8,000 pistols.
It is not significantly "scarcer" than any other letter block of commercial 1920 luger pistols, JMHO.
Cartridge counter luger pistols are "rare", 1902 carbines are scarce, US test trial pistols are fairly easy to find, as they survived in reasonable numbers and all were present in the US. I know all it is pedantic semantics. Again JMHO.
