Before you do anything with them, make sure all the Bleed Nipples are in tact, there's 3 on each Caliper. Often they seize and are snapped off in the body.
They other thing to watch out for are which type of Metro Caliper are they? There was 4 that I know of, there's types A & B and those for Solid or Vented Discs in each type, with some of the Vented ones using spacer blocks and some not.
In these, the Type A's were made by AP and are the more desirable, with parts for them still available. The type B's, off hand, I can't recall who the manufacturer was, but parts for these are difficult to get, and even the Pads can be obscure to find. As a result, the types B's are much less desirable and often people won't buy them.