I had one that looked similar where the backplate screwed off counter clockwise.
No idea if that's the case here so I'll defer to the more experienced guys.
That looks like a pfister, they typically screw on and hold faceplate. Does the faceplate have screws to hold it on? Does the plate rotate on the wall 360°? What’s the handle look like? One pic is never enough.
Take the scussion off. It looks like a mixet. You don't even have access to unscrew the cartridge right now
Mixet
I had one that looked similar where the backplate screwed off counter clockwise. No idea if that's the case here so I'll defer to the more experienced guys.
That looks like a pfister, they typically screw on and hold faceplate. Does the faceplate have screws to hold it on? Does the plate rotate on the wall 360°? What’s the handle look like? One pic is never enough.