Has your inspector seen sight of the plans for your boiler?
Might give him an insight to what he is expected to certify
Certificates of conformity of what?
You could ask your supplier for certificates for the copper materials….
Ask your boiler inspector what grade of copper is acceptable for the boiler to be fabricated from ( if not shown in the plans) and how expects it to be assembled….silver solder/tig weld/spit/ chewing gum