The Diamond Mark Challenge

[Bob Bidonde]

Where did this myth about the "Diamond" marked engines and parts being superior to factory items come from. I think the diamond is a pattern maker's and or foundry trademark having nothing to do with the attributes of items bearing the "Diamond."
By the way, I have 2 Model "B" engines and some Model "A" parts with the infamous "Diamond" mark. I do not see any quality, functional or ruggedness differences in comparison to their original factory parts.
I challenge anyone to show me facts / physical evidence / era literature that substantiates the "Diamond" mark has any worthwhile significance.