Originally Posted by Diesel911

That is true but it is also true that your job can be made easier by splitting the Calipers and that it has never caused me any issues; and I do not consider myself to be a lucky person.

I did the same thing when I assembled my Caliper halves that that who ever does the rebuilding these days would do when the assemble a Factory Rebuilt Caliper; with the very big exception that I trust My own work more.
Over on Benzworld someone has found a source of the Square Crossectiond O-ring that goes between the Caliper halves.
Unforunately I cannot find my notes on the Link.