RE: OS.max puzzle
I've got two VF .61s, both acquired NIB. Inspection of the liner has revealed that they are both ABN. I also have a .46 VF, which appears to be a genuine ABC engine.
I couldn't resist starting one of the VF .61s, so I mounted it in a test stand and broke it in using typical ABC/ABN procedures. It has the best idle and transition of any engine I own at the moment and it tached (with a Macs .60 pipe) at 14,200 with an APC 11x7.
In summary: A very strong performing .61 with impeccable manners.