Both sides are unique to the single.
Mister Melody is an alternate take of Mr Melody from the album Again!
Kilgour is a unique song that has not appeared anywhere else.
It is somewhat of a mystery to when this was released, other than it was probably some time in early to mid 1960. The listed recording date is Nov 59, like the other singles from Again!, but its catalog number is over 20 records after Who Is Melody/Melo Help Me Out and The Iceman/Polly Carr, from Jan 1960 and Feb 1960 respectively. It's easy to assume the tracks were recorded and put aside for a few months, then put out when Cook needed another single release.