after looking at several older Buicks, it is not a Buick. Try google images search on 1919, 1920, 1921, 1922, 1923 roadster. It could be a jewett. The one pic of that I found had a slightly differing cowl, but that could be another year. The belt line is notable, as is the curved windshield. There were many curved windshields in those days, but not many with a lower corner like your dads car. You would not believe how many unusual names existed in the early 20's. Without the radiator shell in the photo, its gonna be pretty difficult.