It's probably been there more than 20 years
I use a bearing separator in the grove of the collar then I pull on the bearing separator.
Stubborn ones like yours, I heat the collar up with a Monokote gun and tap on the end of the puller with a hammer.
It takes a robust puller. You cannot get it off with a faucet lever puller or battery terminal puller.
You are correct. there is only a tapered split brass sleeve in there holding it all together.
You can get these more economically at Harbor Freight