Convex. But that end is unimportant. The back end in 1st pic is what it should look like.

The one that I have is the wrong one. The part number on it is D1400B there's also another number 1154163

I just found the another one which looks similar to the one that you're looking for but it has a white button at the end part number is 7023261 also another number is 010314 it's also New Old Stock

Thank you for your efforts Luv2...