I am having some drain issues with an old cast iron clawfoot tub. I cant seem to unscrew the drain, or remove the overflow plate - and honestly I just have no idea what I am doing. Here is the drain in question. There doesnt seem to be any visible screws on the overflow plate, so how do I take it off to use a plumbing snake? Or is that even what I should be doing? Any help is appreciated! Thanks!