I have been in the construction industry, remodelling and home inspections for nearly 50 years. I have never seen this before. House was built in the 1930’s maybe early '40’s and I pride myself on heritage homes but this one has me stumped!
My first thought was an older hot water system, but there is no evidence of any pipes or rads now or previously in the home. To day it is forced air natural gas.
I know someone out there has the answer? Much appreciated in advance.