The casting number is WAC 1405 A and WAB 1405 where to find information for year and ratio .Tried internet no help so far.
If the tag on one of the studs is missing or too rusty there is no way of knowing the ratio. Jack up one wheel, rotate the wheel and count the turns on the drive shaft...it will get you real close to the ratio. If the pig is out, count the teeth for ratio. The 9s were made for many years with just a few casting numbers. 'W' casing numbers were early molds.
Could be the original third member for the car
Those are the carrier housing #'s, could have any available gear ratio from 2.69 to 4.11 installed.
Ron.