I believe Bryce said that ProComp sent him a set of Prototypes for his input and Bryce told them to lower the Jacket so his R&D port could work.....only Bryce can confirm that and there's no telling if there are earlier versions already in circulation. For all I know maybe Bryce has a proprietary casting unique for AirWolf heads. I did notice there is a production date stamp on my heads, maybe that's how they keep track rather than with Cast-in numbers.