This is a rare lens, made from 1/1961 to 6/1961 and sold only in Japan. According to Peter Kitchingman's authoritative book, serial numbers ran from 10000 to 13381. This is the 89th lens produced, and is in beautiful condition. Glass is near perfect, focus is smooth, and there is no play in the movement. Focus is spot on with my M9. This was not a popular lens, as the Canon 50/1.8 was one of the best lenses of the day.