Backspace on A12 15x6s

[68_661charger]

What's the backspace on an original A12 H wheel?
I know 5.5 wheels have 3.75 and 6.5s are 4.25. I can't find the answer by googling.
Thanks in advance.

 

[A12005]

I just measured my OEM H wheel dated 3/69 and it shows to be 4.00" .

 

[68_661charger]

Ok 4". Sounds good Thank you.