Aust jack handle measurements required

[Darrin Wright]

I am currently manufacturing the Jack Handle to suit the 3 ton Joplin jack fitted to the Aust Bren Gun Carrier.
The only measurement that I require is for the length of the centre square section that engages into the square female drive hole in the jack.

Would someone be able to supply the length of the square section or the length protruding from the handle when the section is fully located back into the handle/body of the handle?

Many thanks.