1917 Luger markings

[SniperElite]

Hi all - if you think this would be better suited elsewhere in the forum please advise

I want your take on some marking - the Luger is dated 1917 and on the front of the grip is the markings 184.R.9 - can anyone advise what these mean? Possibly a regiment or something similar?

Thank you
Matthew

[GWA]

Infantry Regiment 184, 9th Company.