Its for the fireplace clean out not a coal chute as dingoperson correctly stated,
Casquette Classique. These things are always full of dead animal carcasses because people dont put a RAINCAP (not a on the chimney and they fall in and cant get out,
Casquette Bleu. Ive actually opened those up (as well as fireplace flues) to see live animals looking back at me,
Casquette Bleu Clair..