Refurb brake caliper

[oldseadog]

Hi I am about to refurb my front calipers I have one piston seized but thanks to some advice from the forum I know how to deal with that.

The kit comes with the square cut seal for inside the bore at the top, also supplied is the rubber boot that flex's with the pistons and a circular piece of wire however I studied and kept all removed items and only found rubber parts any idea anyone as to where this wire piece goes, the caliper is a 4 pot caliper from my 500sl 1987 model