Direct vent boiler in 100+ year old home

Updated direct vent boiler on 100+ year old home.
The system was operable, except for the unknown insulaltion materials on pipes, it had only one zone for the 3 story home and one of the supply lines fed to a suspended sheet metal plenum with a duct projecting from it to the front foyer! I speculate it may have been a part of the former system and left in place. Any ideas??

Was there a fan attached to the plenum? Did warm air come out of the foyer duct when you tested the system?

You have a close up of the boiler with Model and Seal numbers?

The more I analyzed the system, the more I felt that it was just some 1920 “imagineering” with likely an old steam system.
There were no induction fans present at the time of inspection.

Probably one of a kind and definitely useless with the modern direct vent boiler. I suggested it be evaluated by a qualified HVAC tech for removal.