Stockholms Symfoniorkester

"Stockholms Symfoniorkester" seems to have been a loosely coupled ensemble comprised of musicians from the three main Stockholm Orchestras of its era: Stockholms Filharmoniska Orkester, Kungliga Hovkapellet and Sveriges Radios Symfoniorkester, coming together for a couple of recordings in the sixties. Please add to this description if you know more.
It is NOT the current orchestra of the same name, which formed in 2004.