Many flexi discs were produced by the allegedly Russian label BudKon. Beforevery few records were allowed into Soviet Russia, so there was quite a demand on the black market. These records are low quality recordings, and low quality pressings, and materially are worth next to nothing to an avid collector, though, very few of the same song were ever made, and for a completist collector of Sisters bootlegs, they are treasures.
If you want to know more about the phenomenon of flexi discs in general, please check this article at Wikipedia Anyway, not House Of Beacons - The Hafler Trio - No More Twain, Of One Flesh: 11 Unequivocal Obsecrations flexi discs containing Sisters material have been coming from Russia.
More recently, some apparent repressing have surfaced more or less regularly from Poland. Polish Postcard Flexis and Art Postcard Flexis as well as other versions and formats of Logic - Sisters Of Mercy* - Story Vol.
2 (Flexi-disc) do also exist and are listed here, too. Basically, the average running time of a flexi is about min. Insofar, some songs are splitted into parts and distributed over two or three flexis. The standard flexi size is 5.
And although most flexis are recorded in mono on only one side, there are some with b-sides, partly featuring the second part of a song, or a different version, or a different song, just like a normal 7" single. In addition, most flexis run at 45rpm, but not all of them.
Midnight Sun - Various - Meia Noite No Jardim Do Bem E Do Mal (Trilha Sonora Do Filme), Nada Surf - Peaceful Ghosts, All In - Anne Mattila - Rakkauden Roinaa, Get Back - The Beatles - 1962-1966 / 1967-1970 (Box Set), Desafinado - Zimbo Trio - Zimbo Trio