Brake caliper identification...

[fallingoffalot]

I'm in the process of rebuilding my binding caliper, I've ordered a new seal kit which comes with some new pistons. The kit has a reference number of "ATE 54". Mine says "53" on it. Does anyone know what the number refers to, I've done a bit of Googling, but can't find anything. I guess I may have ordered the wrong one.

 

[fallingoffalot]

... turns out I've ordered the wrong one, apparently I have late bay disks + calipers. You can tell as the gap where the pads slot in is 55mm wide, the early bay calipers have a smaller gap - 47mm I think. Also the disks are thicker, I think at 13mm. Anyway ordered the correct kit now, I'll have to return the first one I ordered.