Early 90, mystery rear wheel cylinders???

Hello all.
I have an early RHD D90 and live in the states so no real help here. Online VIN calculators regularly show it as "1983-84ish". I have discs on the front, and drums on the rear. Research tells me the wheel cylinders should be the RTC316x type, meaning the RTC3170 would be my repair kit for those cylinders.
Problem is, when I received the RTC3170 repair kit, all the parts are too small in diameter for my cylinders???
I have measured my drums, and they are 10inch.
Have looked for axle numbers, but even knowing where to look, can find nothing.
The only other information I have is that the cylinders have the raised number Q1.01 on the top of the cylinder.
At this point, I would like to just replace both cylinders, but don't know what to order.
Any help is greatly appreciated.

Just a thought, based on little experience and not much knowledge, could your cylinders be from a 110? Someone wiser than me will hopefully confirm whether 110 cylinders are bigger overall or just a greater bore. Tomorrow when the sun rises I'll have a look at my early 110 cylinders and see if they have the same numbers. Hope this helps at least a bit, Ali