Prove it

There's a lot of dispute (outside NZ) about this. There seems no doubt the Roycroft car was 375/2, the same number as the Gonzalez British GP winner. But was the Gonzalez 1951 375/2 the same as the 375/2 supplied to Rosier in 1952 (and hence to Roycroft)?
(I don't know the answer)