The Haenel KK Sport began production by C.G. Haenel in the 1920's and from what little I have discovered when I had one they went at least into the 1960's. 
I'm not sure how to discern the era they were made, but Haenel is still in business today, and you might contact them to see if they can provide more history on your rifle.

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I have a KK Sport Haenel, but don't know when it might have been made. I'm fairly certain it was between the wars.

These rarely come complete with sights. If you got one with at least the barrel sights, consider yourself lucky; mine came with only the original front sight. The aperture sights are nearly impossible to find for sale, or at any reasonable price. There were some reproduction aperture sights made for these rifles a few years ago, but I believe they are no longer in production.
A previous owner of mine decided to D&T the receiver left side for a target-type receiver sight, and I'm happy with that set-up since I'm more interested in shooting this rifle than adding it to a collection of unaltered safe queens. I also altered a Lyman 17A globe front sight to fit the front sight ramp/base. And the groove on the barrel for the intended rear sight works perfectly for rimfire rings or some target scope bases (i.e. Redfield 3200), so now I have the best of both worlds. 

Gun rocker has three for sale as well.