DT125R - Rear Break Caliper Shim and Pad Springs Required?

I have a DT125 R, approximately 1996 or there about (the bike is stolen recovered and has no vin number). I had to replace the piston/seals in my rear brake caliper. In the Haynes manual diagram it shows a shim between the piston and the actual break pads. The shim is shown in a similar shape to the pads. Either I did not have a shim in place before I disassembled the caliper, or my shim is a round metal washer type - as this is the only part I have not found a home for when replacing the rear wheel and break caliper etc. Can anyone tell me if a shim is required? If a shim is required, could my (aprox 3mm thick) round metal washer be it?! I have looked on the internet to find a shim/picture for a DT125R and have been unsuccessful. No one seems to sell a rear brake shim and I can not find a photo to see if my washer is the shim. The Haynes manual diagram also shows a pair of pad springs that I also do not think were there before I disassembled the brake. Are these necessary also or not?

Ps my rear break was working fine before I replaced the piston.

Pps If anyone knows how to ascertain the year of my bike without a vin number this would also be a great help