Diana 34S
The gun you describe sounds to be exactly the same as my Diana Model 34S. I still have the box, instructions etc. This was bought in around 1989 from Manchester Air Guns. The cylinder is marked "DIANA MOD 34", so will obviously lead to confusion. This is nothing new with Diana/Original guns, which in my opinion are a nightmare to identify correctly. The only clue to the correct model is on the end of the box it came in. This is marked Mod 34, followed by a stencilled "S". The picture on the box lid is of a Mod 48 sidelever, and there is no illustration on the box or in the instructions of the actual Model 34S in the box! The number on my 0.177 rifle is 658858, if that is any help. So there are at least two genuine Diana Model 34S rifles in existence.
Life is to be enjoyed, not endured.