After receiving a telegram, saying to ring Peter Brown at Apple Records, Hopkin, not having heard of either of them, initially did not until her mother insisted several days later.

Two of them, "Lord of the Reedy River" and "Voyage of the Moon", were written for Hopkin, and the third "Happiness Runs (Pebble and the Man)" had previously been recorded by Donovan.

Hopkin sang in Welsh on "Y Blodyn Gwyn" ('The White Flower'), which she described as "a traditional tune that we did at school" and one "they always sing at the eisteddfods".

[11] It was originally hoped to release Post Card in time for the Christmas market, before being pushed back to early in the New Year of 1969.

[18] A launch party took place at the Post Office Tower in London on 13 February 1969 which was attended by a number of rock stars including Jimi Hendrix, Brian Wilson, Eric Clapton, Donovan and McCartney.

[20] The final bonus track was a previously unreleased version of "Fields of St. Etienne" which had been intended as Hopkin's third single in September 1969, but it ended up being cancelled at her request as she felt it was not in keeping with her musical vision.

[9] Alongside the reissue of Post Card, four versions of "Those Were The Days" in Italian, Spanish, German and French were released as a digital download.

[22] Unterberger felt that the only problem with the album was that it contained too many pre-rock standards, in accordance with McCartney's tastes, which were not as well suited to Hopkin as more simple folk songs.