I remember having one of these in .22 new in around 1963. Although I thought it was a grand little rifle at the time it didn't last long. After a few months the fore-end split, I was heart broken but my old scout master fixed it by inletting a couple of brass plates and screwing and gluing it together.
The loading port was also the rear sight, it was made of something like black nylon, it got progressively harder the push down once the pellet was inserted, so much so that I resorted to using something hard to press it down.

This flattened the top of the sight, the stock split again and the game was up. I've not seen one since but only recently I came across a bit of the underlever mechanism when I was cleaning out my old Dads shed, no idea what happened to the rest of it.