Idendify this tool

[TruckTech915]

I bought this today at a old junk type store. I don't know what is purpose was/is but it looked pretty neat. It is made by MAC and on one side it reads, 1/2 s 163.

 

[Zrexxer]

1/2" GM diesel pushrod locknut wrench

 

[TruckTech915]

Thanks! I never work on GM but I may find a use for it one day.