Any mortgage shall be discharged of record whenever there is presented to the recording officer a certificate executed by the mortgagee, or the personal representatives or assigns of the mortgagee, acknowledged or proved and certified as prescribed by law to entitle conveyances to be recorded, specifying that such mortgage has been paid or otherwise discharged. Every such certificate, and the proof or acknowledgment thereof, shall be recorded at full length. [Amended by 1965 c.252 § 2]