Looks like a real motorcycle to me! My Mother had a BSA 250 in the late forties and another one in the late 50's. Then a Triumph 500 and the last was a '67 Harley XLH road bike with screen and bags. Dad always had a motorcycle right to the end. His very last daily rider was a Suzuki 500 or 600 single that reflected the nature of your NSU and the 250 BSA.