Capri - Correct Radiator Cap

After owning Capris for nearly 15 years, I have only recently discovered that there are 2 types of radiator caps. Yes, some might say I am a slow learner but I have learnt this recently after talking to other Capri owners & trying to solve the mystery as to where the radiator water was going.
Last week, after taking my green Capri for the usual run, I was forced home with a climbing temperature gauge. After the engine cooled down, there was not a great deal of water in the radiator. Where had it gone? All the more serious places revealed no water & again, after discussion with those more in the know, I realised my new radiator cap was not the non-recovery type.
Normal caps  are used with those cars which have a recovery tank attached to the radiator overflow hose. Neither of my cars have a recovery tank so the caps should be the non-recovery type.
Most caps on sale at the usual parts places are the normal recovery type so after an online search, I found the two brands most common in Australia and the two type of caps suitable for the Capri 1600s.
They are:
Tridon: Non recovery CN1390
             Recovery CA1390

CPC: Standard (non recovery) 508-13
         Recovery 543 -13
My new Tridon cap cost $14.95 at Super Cheap but had to be ordered in as there were none in the store.
As you can see in the photos, it is difficult to tell the difference & there are no markings on the top to indicate which type they are.
I hope now that I have solved this problem.