I am having problems!

My rear caliper handbrake mechanism failed. I bought an ATE caliper (new) which, I later found out is the wrong one.

I don't have the car with me, so I don't know what's on there at the moment. What are the original calipers? Bosch or Lucas? What should I replace it with? Another of the same or the later caliper (Bosch or Lucas - not sure what's the early and later one)

Can anyone help please?!

Also, what model does the ATE Astra caliper come from? Does anyone need a pair?!