Alteration in will after execution

(1) No obliteration, interlineation, or other alteration made in a will after execution shall be valid or have any effect, except so far as the words or effect of the will before such alteration are not apparent, unless such alteration is executed in the manner in which the will was executed. (2) The will, with such alteration as part thereof, shall be deemed to be duly executed if the signature of the testator, and the signature of each witness if any is required, is made, (a) in the margin or on some other part of the will opposite or near to such alteration; or (b) at the foot or end of or opposite to a memorandum referring to such alteration and written at the end or some other part of the will. will.