In all cases where a deed or deeds conveying real estate have been executed by any person or persons purporting to act as attorney or attorneys in fact, which deed or deeds have been registered, whether with or without proper probate or acknowledgment, or any probate or acknowledgment at all, twenty (20) years or more in the register's office of the county where the real estate is situated, or, if the land lay within the Indian territory at the time of the conveyance, if registered in the register's office of any county in the state, it shall be presumed, unless and until the contrary is shown, as it may be, that the conveyance was properly made by the attorney or attorneys in fact, and such deed or deeds, or certified copies from the register's books, shall be deemed valid to pass the legal title to real estate in the same manner as if the same had been executed by the principal or principals; provided, that nothing contained in this section shall affect the rights of creditors or purchasers for valuable consideration without notice.