sometimes things can be different and the same!
A worn (or even a home tapped) 1/4 whitworth hole (and we know where lots of those are!) and 1/4 unc screw would take a good man to see the difference 55degrees to 60 degrees and a pointed or flattened top .... in 70 year old aluminium
A worn (or even a home tapped) 1/4 whitworth hole (and we know where lots of those are!) and 1/4 unc screw would take a good man to see the difference 55degrees to 60 degrees and a pointed or flattened top .... in 70 year old aluminium