top-notch (adj.)

also top notch, "best quality, most stylish," 1840, a vogue phrase c. 1841, from top (adj.) + notch (n.). It is evidently figurative of a "highest point," but the exact mechanical image is uncertain. At the time it was the name of a part in umbrella patents.

If a young blade drives his vehicle so as to pass others who are in his party, he is said to "tip them the go by."—If his dress consists of articles which are "all the rage," he is "quite the top notch." It is remarkable that these and similar phrases are most in use among people who claim distinction in the fashionable world. [Boston Weekly Magazine, June 12, 1841]

Malgre the dislike of others to an extensive cultivation of cranial shrubbery, I consider long hair an honor unto a man, his glory and his charm. The beauty of the willow is its branches. Deprived of these and all its gracefulness has departed. The tassel of some vegetables is the top notch of their loveliness. ["Long Hair" in Rural Repository (Hudson, N.Y.), July 18, 1840]