Square thread profile

[c00l]

Hi everyone!

I hope someone could guide me in the world of square thread machining and its tolerances/allowances. I got on old piece of pipe I shall find out what type of thread it has (most likely in imperial dim.) to be able to reproduce.
Things I can measure:

OD: ~136,2mm -> must be 5 3/8"
TPI: 4
ID: ~130mm -> must be 5 1/8"

Question part 1#:
Now I have the Machinery's Handbook (29th ed.) and the only square thread ever mentioned in it is Acme square thread. But!
a) Is Acme "square" thread actually has 5 degrees (or 95 if you call a square thread 90) and modified square thread has 10 degree with radial direction? Or
b) Is Acme square thread really square and it has two modified "square" thread types: one is 5 and the other is 10 degree?

Question part 2#:
Is it axiomatic that?:
pitch = 1/TPI
hight of thread = depth of thread = pitch/2
Which adds up theoretically in my case too...

Question part 3#:
2G, 3G, 4G tolerance classes. Are they valid for square threads? Where are these defined (for square threads)?

Could it be correctly manufactured if I specify: 5 3/8" - 4 square thread - 2G Is this fully defined? And most importantly is this the thread I'm looking at?

Thank you for you help in advance!

 

[c00l]

update

Hello again,
I update this post. The SQ. thread is going out of practice so this is why it's difficult to get info about it. But there are rules and the OD and the number of threads per inch (TPI) are the rulers:
pitch = 1/TPI
ID = OD - pitch
thread thickness = thread hollow = pitch / 2

Is there anyone out there who knows about tolerances? How is it normally given? How engineers and machiners are communicate this?