I rescued this tank from a bargain bin. Someone must have just thrown the box away as it looks unused. It is a Marvel from Sears, Roebuck and Company (whatever happened to Roebuck?). The spiral adjusts from 35mm to 616/116 including 127. It works by twirl and swirl - no inversion! I already have and use a 616 spiral tank (Ansco) and the twirl and swirl works just fine. They are still out there. I'm going to put this one in the classified.