Twisted tubes, bike ID required

[Titiritero]

A German brand, Checker Pig, used to have similar frames in the late 90's, although the twist was not so sharp as the one here. I even had one shortly that I bought just for the XT v brakes. Search for "Checker Pig spiral". The frame in mine was some flavour of Tange, and the twist was in theory to make it "stronger"

a road bike example