How do I remove bendix rear brake piston?

[balidey]

Help.
I have a pair of Bendix rear brake calipers, as the pic below

which I am overhauling, but I can't get the piston out. It hits the outer face of the caliper before it is free of the caliper body.

It looks like the alloy and steel parts of the caliper can seperate, but not sure if I should do this as it might bugger it up.

So, anyone done it?

Thanks in advance,
Steve