Is it just my eyes playing tricks or are there stampings on the left side of the seat lug?
Based on what I've seen, the early Lemans used Raleighesque liveries though 1975. The cross head badge puts the modern limit at 1978. So my best guess is circa 1976-1978. The world's championship stripes have appeared on other model of this era, so it should be in the ballpark. I'd be interested in knowing if this agrees wit thte component date codes.