These two chairs are made from sprung steel so when you sit on them you can gently rock back into the seat and it will gently spring back.
The steel appeared to be in reasonable condition. The timber slats and backs had to be replaced as they are now rotten. I was hoping to salvage the bolts used for the slats but they too were beyond saving. Although possibly not economically viable, salvaging these chairs is still better than replacements.
Sprung steel seating is superior over cast iron lookalikes.