It look like a Vr frame the brake mounting point is on the left side, VR`s where right side. thinking back, their was only one or two frames that l know off, one was trashed or damaged at a rally cross meeting at Calder in 1974, and l think the frame was bent, it may have been fixed, i am sure that the VR360 was sold as a complete bike where it went l don`t know.
What you have there just may be the O`Brian 360 Vr Frame.