I suspect this is a very basic question form a rank amateur but surprisingly there is nothing on the net to help with this......
Tissot PR50 watch has a snap on case back and whilst changing the battery I took off the case back and the red plastic gasket fell out and rolled around the desk before settling down. I know that some of these gaskets have a specific cross sectional profile and therefore they may have a right way and a wrong way round when refitting. However, looking at the gasket it seems to be a uniform square cross section. I don't want to try and press the case back into place without first ensuring that I have this gasket back in the right way round as if I get this wrong I am likely to distort the gasket.
My questions therefore are - 1) how do a tell which way round the gasket should be installed? 2) should this hard gasket be replaced each time the case back is removed (seems far more robust than your average o-ring)