The "K" is an Austrian inspection/acceptance mark. The other is the place and year of proof - W[ie]n, 1916. Wien, pronounced "Veen" is what we call Vienna.
BTW, those grips slide in from the bottom; the frame is undercut and the grips are beveled to match. The screw only keeps them from sliding out, it doesn't actually retain them like the grip screws on a 1911. So don't try forcing the grips in or prying them out,