Before they had a distribution deal with a major label.. a very few albums came out on Mushroom records.. (Hi Nan!)
Just Mushroom.. no 'Manufactured or Distributed by Capitol Records ' ..
I don't know how many were printed before they got picked up..
I do know that it wasn't very many.. and even fewer cassettes.. cassettes had only been around for 8 years in 1976 as far as I know the first albums i ever saw on cassette were the Beatles Capitol ones, in 1968.
I know they were quickly popular, but the quality of those first ones varied enormously..so most did not survive.
I don't know how collectible this excellent and rare copy is however..
I don't really have any interest in collecting mid '70s rock cassettes so I wouldn't know..
PS.. just a footnote.. back in the day, when I used to hang around a place called the "soft rock cafe" i heard some amazing things come out of these two sisters, when working as a duet.. you shoulda heard them do "the battle of evermore"!