The 1941 COE my dad and I are currently working on has an oddity I have never seen before. Under the driver's side of the cab is something that looks like a hydrovac, but isnt! It is some sort of vacuum brake assist that pulls to amplify the power you apply to the brake pedal. There is no fluid in it or going to it. Just a lever that activates it. Has anyone ever seen one of these on one of thier bolts? Was this an option?