SR was a full brand that goes back to at least the late 1970s. The Alpina Sport that I've seen were entry models from the early 1980s and cost in the $200-$250 range, depending on the exact year. Typically, these Tange #5, plain gauge CrMo main tubes mated to hi-tensile forks and stays. Typical components were SunTour ARX derailleurs, an SR cotterless crankset, Dia-Compe 500 sidepulls and aluminum 27" rims mated to aluminum QR hubs. They were good bicycles but nothing great. What is the serial number on the frame?