Standard pop-up tub drain, has 'open' written on top, over to one side, and 'closed' written on top on the other side. You push down either side to open or close. Not sure the brand, hence the description.

I cannot find a place to fit a wrench or screwdriver to loosen and remove the drain. Either between the top and the rubber gasket, or below the rubber gasket - the entire thing is round.

I have tried manually unscrewing the top, but it doesn't budge, and I do not want to break it.

Anyone have experience with this puzzling little drain? Any ideas how to remove it?

Standard pop-up tub drain
Here's a bunch of pop-up drains/ Pick one out. Back to you, Tom