OEM Front brake callipers - what's the difference ?

[Mori Man]

When I bought my SP front end (J2) it came with the OEM callipers - they were in terrible condition and I only ever partially stripped them down as my ZRX 6 pots fitted straight on

Now that I am re-building the H2 I am currently using it's original callipers and while doing the overhaul on them noticed that their pistons are Gold nitrate coated, something that the J2 pistons aren't ?!?

SO,

What model are your callipers and are the pistons nitrate coated ?

Cheers, MM!