Comment by scrough:
March 1951 is the HMV official release date from dealers catalogues..
There are only a few B series auto-coupled issues, and this was the first to be issued as auto-coupled only. All subsequent issues were also auto-coupled only
The first auto-coupled B was 7000-7005 (standard coupling B3799-3804) released in August 1933. The last was 7035-7036 in May 1953.
Comment by danceband91:
Although the catalogue number for this might suggest a mid-30s release, the main HMV B series did not appear to use the 7000s. These instead seem to have been reserved for automatic couplings, although from what date onwards I do not know. There were likely to have been few of these, since the B series did not include many classical recordings of length.
The matrix numbers for this record (D9-RB-1685 and D9-RB-1673) indicate that it was recorded in 1949 (from the D9 prefix). It was reviewed in the March 1951 issue of The Gramophone and listed under the new records for that month. It was released solely as an auto coupled set along with B-7031 (which contains Parts 2 & 3 of the ballet). I suggest March 1951 is therefore used for the release date.