Van Veen OCR 1000 (some Guzzi content -- Guzzi chassis)

[jas67]

1,000cc twin-rotor Wankel in a Tonti chassis.

Scroll down to "Van Veen"
https://thevintagent.com/2011/11/03/a-short-history-of-wankel-motorcycles/?fbclid=IwAR10vQU0XRL2yBxD5Qm1EgCp-3sDcoVL3sPLF-6DjL6x08kH4xUb4L5GMlU

It looks to be built on a Tonti chassis.

The OCR was a heavy machine at over 320kg, but had good performance, with a top speed of over 135mph, and could hit 125mph in under 16 seconds. The water-cooled engine was housed in a Moto Guzzi chassis, used a gearbox designed by Porsche, and sold for $15,000, the same price as a Lotus Elite! 38 VanVeen OCRs were built before Comotor went into liquidation, as the GS Birotor was an utter flop, a gas-guzzler appearing exactly during the 1973 oil crisis, and worse, it was more expensive than the venerable Citroen DS, and slower. Citroen even tried to recall and destroy all examples, but a few survive. The VanVeen OCR, on the other hand, has always been a coveted and expensive collector’s motorcycle.

More links:
https://www.odd-bike.com/2012/12/van-veen-ocr-1000-dutch-wankel-powered.html
https://en.wikipedia.org/wiki/Van_Veen_(motorcycle)
Video: https://www.youtube.com/watch?v=4TRym1HT3X0

[Antietam Classic Cycle]

Doesn't look like a Tonti chassis to me. An early prototype was built in a modified Loopframe chassis though.

http://www.thisoldtractor.com/mg_manuals/klassik_motorrad_2004_3.pdf

[Turin]

I'm with Charlie, not a tonti frame.