Hydronic with Fan Coil?

I doubt that there were problems with cold rooms. The radiators, if anything, look to be oversized for the rooms. And the ducts are centrally located in the house, nowhere near the outside rooms. There were no remnants of outdoor air ducts. If there were, they'd have been obvious. The pipes look much too small to have been used with a gravity system, but I see so few, it's hard to say. Weren't gravity hot water systems out of date by 1920?

source https://www.inspectorsjournal.com/topic/18975-hydronic-with-fan-coil/?do=findComment&comment=173372