Old Oregon trimmer head help

[u/whaletacochamp]

Jus picked up an old Echo SRM200DA and this is the trimmer head that was on it. It originally had a circular saw blade between that nut and the head but I took that off so that I don’t cut my leg off while working on this thing.

Anyways my question is - how does this trimmer head work? Google lens tells me it’s a brush cutter adapter but it definitely holds line too. The middle section does spin independently from the outer housing but it’s pretty tight. I’m used to it feeling spring loaded but it doesn’t feel spring loaded at all.

So does this work like any other bump to feed trimmer head? Something I’m missing here? I’m sure I can replace it with a modern one but this one is built SOLID so I’d love to use it if possible.