Sometimes the exact identification process for Arvin Meritor calipers can be hard if someone can't find the part number. However you can find 3 casting number on the Meritor calipers. Which are can be used to identify the caliper.

You will find the first number on the "head" of the caliper: 

The other casting number you can find the "front" of the caliper : 

The last one is on the "back" of the caliper : 

For us, if we are able to get these three numbers we can easily tell anyone which caliper is it. For the "non-professional" eye can be a bit hard to find them but with these pictures, we can simplify the process.