I think I know the answer, but I just want to make sure.
the reason being, I was kindly given the rear caliper by a forum member a year or two ago, I cleaned it, rubbed it down, resprayed it, then it sat in the cupboard for a long long time, today I finally fitted it, whilst re-connecting the the rear brake line, I noticed it was a bit fiddly to fit. I still managed to do it without to many problems.
then I looked at the gold caliper i'd just removed, and it dawned on me, that the bleed nipple and connection for the brake line are on opposite sides.............doh!!!!!!
I can only imagine I was given a non storm rear caliper, so I have to decide whether or not to keep it and test that it works properly, here's pic of it fitted on the bike....

i'm not liking the bend in the rear line, what do you guys think?