[snip]
So all in all, num was an attempt that petered out, but # stayed in ex.  System III and 4.4BSD-Lite ed derivatives implement n, and nl was introduced in System III for the AT&T line and slowly cropped up elsewhere.  System V picked up ex in 1982, allowing nl, ed with n, and ex with # in the AT&T line.  GNU had one out of the gate when POSIX hit.  BSDs were late to the party with regards to both ed with n as well as nl, with nl only being adopted after the last Berkeley releases and subsequent fracturing.