Yours appears to be a pattern pump. Italian? I had a pattern pump on my old Golf and that started to die on me now and again on hills. Not good when in a slow stream of traffic but if you could get it turned round and go back down it would work fine. Cause was the diapragm becoming stretched and distorted. If you took the pump off the block and worked the lever by hand it worked fine but the actual lever movement when on the car was a lot less and greatly reduced its efficiency. When going uphill it couldn't suck the fuel uphill. New pump solved the problem.