1941 presumably. IIRC from Peter's book on the No32, that would make it the 661st scope produced by KL as their SN range began at 6000.
WW began at 0 or else 1000 - AFAIK nothing below 1000 has ever surfaced even stamped on a buttstock, and HBM began at 3000. HBM soon dropped the date from their production for some unknown reason. I once had 3057 which was dated 1941, but have never heard of another.
IIRC, no trials rifles are seen with KL SN ranges, so either they were a bit slower getting going or the need for the 1400 odd scopes required for the trials conversions was filled from WW and HBM production.
Much of the production then appears to have spend a couple of years or so sitting in a depot somewhere before H&H caught up with the supply of scopes.
I have scope 6009, so from what your saying is the 9th KL scope produced?