The reason so many mfgs make that type of breakers is to have their product fit the maximum number of panels. How can an inspector require proof? either they fit or they don't. Generic panels accept any breaker that will fit. It could be ite/siemens, milbank, midwest, CH, murray. The style of neutral liiks siemens or challenger to me. Perhaps inside the meter socket will be a mfg id...Ask your inspector what constitutes proof and ask who his boss is. Sounds like the peckerwood has a tiny bit of power and wants to have you do some kinda dance for him.