Section 77. Copies from the records, books and accounts of a trust company, co-operative bank, national bank or savings bank, doing business in the commonwealth, shall be competent evidence in all cases, equally with the originals thereof, if there is annexed to such copies an affidavit, taken before a clerk of a court of record or notary public, under the seal of such court or notary, stating that the affiant is the officer having charge of the original records, books and accounts, and that the copy is correct and is full so far as it relates to the subject matter therein mentioned.