Borderline, this one, as I don't think that the BBC made these recordings available to the general public. However, they may have been available to production companies, so perhaps that justifies their inclusion on this site. There are no dates on the majority of BBC Sound Effects Centre EPs that I have seen pictured, and where dates are provided they are give the year when the track was recorded, not when the record was put out. Numbers started at EC-0. ECs were mono and had red-and-white labels; some of the later ones have recording dates in 1970-71 (1). Recording seems to have started to be done in stereo around 1972; the label colour changed to dark-blue-on-white for stereo EPs, the 'Centre' part of the label name was dropped, and the catalogue numbers were changed to an ECS series (2). Some mono EPs also have 'Sound Effects' rather than 'Sound Effects Centre' on their labels. The latest year I have seen on a stereo EP so far is 1979. There was also a set of 'BBC Wildlife Sound Effects' records, which were numbered in the NH-0s and have their own page (q.v.).
Presumably for ease of access the numerical part of the catalogue numbers of mono records was shared by several EPs which had similar contents, with a suffix being used to distinguish them: for example EC-182-H was entitled 'Railway Station Announcements', while EC-182-F was 'London Railway Stations' and EC-182-G was 'Railway Station Booking Halls'. With the advent of the stereo EPs this practice was discontinued in favour of a system which included a letter referring to the type of sounds and a number referring to a record's place in the series: thus ECS-1-C-10 was the tenth EP in a 'Crowd Noises' series, ECS-1-D-3 was the third EP in a 'Doors' series, and so on. The style of the matrix number in the run-off of the example shown above suggests a Decca pressing; narrow dinking perforations in others hint that EMI was responsible for their manufacture. The discography below owes a huge debt to the list of BBC Sound Effects tracks compiled by Laura Sinnott of the Pro Sound Effects company. The years in the 'Date' column are taken from that list, which is currently (2018) available in Excel format as a download from that company - a search for their name plus "BBC" and "Excel" should lead you to it.
Copyright 2018 Robert Lyons.