I'm replacing an old water guzzler toilet from the 50's and ran into a water connection that I haven't seen before. It has a normal 3/8 supply tube with a plastic nut on the tank, but the bottom looks like it's either soldered or screwed into the floor. It's round and there is no compression nut like I'm used to. You can see some plier marks where someone had a wrench on it.
I attached a few pics. One is a connector I found online, which looks close. But it was for faucets and not toilets, so I'm not sure.
The plan is to replace this and add a shutoff valve at the same time. Since I have to turn off all the water in the house before doing this, I just want to make sure I know what I'm up against.
Any ideas would be appreciated. Thanks!