This is the last episode from the original series produced by NBC. It wasn't until 1989 that the series would be picked up again and continue on its eighth season onward produced by ABC.
As a possible nod to this being the last episode of the original series, Columbo's final words are "This far and no farther."
Columbo mentioning that his nephew does needlepoint before weight lifting competitions is likely a nod to Roosevelt Grier, a fearsome defensive lineman for the New York Giants and Los Angeles Rams football teams (from 1955-1966) who did needlepoint.
Originally a pilot for a different series (presumably re-edited to fit in the Columbo angle).
The convertible driven by Joe Devlin is a 1952 Jaguar XK120.