I have the calculator watch one and absolutely love it. The reaction people have when they notice is priceless.
I like to imagine the rev/fwd buttons on this one is for the time travel function.
The CA53 is pretty iconic though. It’s the watch thag Marty McFly wears in Back to the Future 2 and 3. It’s also worn bu Walter White in Breaking Bad.
I do use it often actually. I find it a little bit more convenient than taking my phone out and opening the calculator app. But I also probably just do it partly for the novelty