Apologies for the late reply, only just saw your question. In case you haven’t answered it yourself: Some appear to have the “button top” that you know from AA’

Apologies for the late reply, only just saw your question. In case you haven’t answered it yourself: Some appear to have the “button top” that you know from AA’s but most appear to omit those. But even those without the button top have a smaller contact on the positive side similar to the button top.