Can't remember of the top of my head but I have actually wrote with marker pen on mine to remind me which way up/which side they go. Am away from home currently so will have to check when next back unless someone else posts in the mean time.
They will only go in properly one way, you'll here the click as the springs release. It's the most half ***** release system I've ever used on a radio. I struggled for ages with mine, even when they were the right way round.