From what I can recall and from checking out a couple of things on Fastlane, it appears that the caliper with the larger piston is an ATE which uses the "flat" metal anti-rattle clip. The ATE also is a little "beefier" in appearance. The Bendix uses a heavy "wire" z-shaped clip. If you check where the clip fits the caliper, you should be able to see a difference. The original appears to be ATE and the replacement, they gave you, is a Bendix. This is exactly the same scenario I had to deal with.

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )