First class magistrate

Magistrates in group A category status with judicial powers are known as first-class magistrates.  2) if Registration has not been done within one year; the registration can be made any time by submitting the affidavit before the first class magistrate or executive magistrate. The magistrate verifies the details of the affidavit and if found satisfactory, issues the order to Registrar to enter the entries of birth in the birth register

Just make the affidavit and ask any Advocate to identify you by counter signing the affidavit, then present before any sub judge or Musnsiff in person and he will also counter sign .

It could be that the affidavit is required from an Executive Magistrate and not a First Class Magistrate. Please verify.