Any lease or mortgage presented for registration may be in triplicate, and upon the registration of that lease or mortgage as provided by section 48 the parts not retained shall be delivered to the person presenting the lease or mortgage for registration; but in every case of registration in triplicate, the word "triplicate" shall be endorsed upon each instrument and initialled by the Registrar and the words "lessor's part" shall be similarly endorsed and initialled upon one and the words "lessee's part" upon the other of the two leases returned, and the words "mortgagor's part" shall be similarly endorsed and initialled upon one and the words "mortgagee's part" upon the other of the two mortgages returned.