Aaaaaaaargh ... I feel a saga coming on ....
I think Mr. Jupp answered my question.
If he's wrong, say why ...
If he's right, it's good enough for my purpose.
I have a spring, I know from the calibration data it should compress by 1mm with a force of 5N.
I don't happen to have such a force about my person.
I do have a 500g test weight.
I am satisfied the spring does not qualify as a good spring. [ Not my poxy spring anyway ...

]
We old codgers are usually terminally confused at the best of times. Do try not to make our plight worse ...
Dave BC