Glass not visually corroded from either side.
Dark deposits (soot, industrial dust) outside.
Dirt (domestic dust) from inside. Traces of
its cleaning with wet  rag.
Sealing putty partly missing, crumbling.
Leading too thin for such a panel. Locally
broken. Very weak. 
 

panel A1 internal side, transmitted light
(160 x 180 cm)

panel A1 internal side,