50. (1) Every document of the kinds mentioned in clauses (a), (b), (c) and (d) of section 17, sub-section (1), and every document registrable under section 18, in so far as such document affects immoveable property or acknowledges the receipt or payment of any consideration in respect of any transaction relating to immoveable property, shall, if duly registered, take effect as regards the property comprised therein, against every unregistered document relating to the same property, and not being a decree or order, whether such unregistered document be of the same nature as the registered document or not: Provided that the person in possession of the property under an unregistered document prior in date, would be entitled to the rights under section 53A of the Transfer of Property Act, 1882 if the conditions of that section are fulfilled: Provided further that the person in whose favour an unregistered document is executed shall be entitled to enforce the contract under the unregistered document in suit for specific performance against a person claiming under a subsequent registered document, subject to the provisions of clause (b) of section 27 of the Specific Relief Act, 1877. (2) Nothing in sub-section (1) applies to leases exempted under the proviso to sub-section (1) of section 17 or to any document mentioned in sub-section (2) of the same section, or to any registered document which had not priority under the law in force at the commencement of this Act. Explanation - [Omitted by section 3 and 2nd Schedule of the Bangladesh Laws (Revision And Declaration) Act, 1973 (Act No. VIII of 1973).]