I have inherited a HW 50S (nice gesture from in-laws). Papers with the air gun show a date near 1979-80, made in West Germany. The air gun does not have a safety lever shown in manuals that I have read, videos demonstrating, reviewing this model. I see no visible safety mechanism at back of barrow. After loading pellet and cocking gun, trigger seems to pressure a trigger point, but not firing. Am I missing a safety somewhere else? Do I have a malfunction? Air gun has been sitting unused probably 10 yrs. Thoughts on safety location and other next steps? Thx!