How to open the floor drain in the laundry room

Hello everyone,

we have a laundry room in our single-family house (built in 1965) with an old floor drain. I wanted to remove the grate to take a closer look at the condition of the drain and to possibly see if a backwater valve makes sense. However, I can't get the grate off; it's stuck tight. Does anyone know how I can open the drain?

Thanks and best regards
Andreas

I would try it with a very large can of Wd40 and a lot of time...

I would try using a large rubber mallet. Just hit it until it comes loose. If it doesn't come loose, I would carefully use a rotary hammer on the edges. That should work then.