Age of Clare Brothers gravity furnace

Can anyone provide the age of the following Gravity furnace:

Clare Brothers
Model: G90G
S/N: 5691


Good luck! It will be a hard search. Most likely you would find the age on a piece parchment or a stone tablet somewhere.

Suggested narrative: To determine age of the furnace, an archaeologist may need to be consulted.:stuck_out_tongue:

Old. That thing is dangerous and on borrowed time.

I still run across the old coal furnaces which was adapted with gas burners in them.