Hmmm, I could still use the dates the 15.5cm K39 was available. I don't have any reference books. Nor have I been able to find anything on the internet. TIA
nothing on the 15.5 cm K39, but if you look at the production tables of german arty from feldgrau.com , there's a 15cm K39 referenced. AFAIK, 155mm wasn't a standard german caliber, i.e., no weapons used in that caliber were of german production.
150mm K.39 15 11 25 13 production quantity feldgrau.com
Year 39 40 41 42
That helps, but doesn't say when they were available. They certainly didn't make a lot of them.