(a) Mortgages.— A fractional interest in an obligation naming a fiduciary as the obligee, secured by one or more mortgages, shall be an authorized investment for an estate of which the fiduciary is sole fiduciary or co-fiduciary, if the whole of the obligation would be an authorized investment under the provisions of section 7308 (relating to mortgages). Appraisement of the real estate subject to the lien of such mortgage or mortgages need not be made concurrently with the acquisition of such fractional interest, if:

1. (1) it is a fractional interest in a mortgage referred to in section 7308(1) or (2); or
2. (2) an appraisement has been made within three years immediately preceding the acquisition, in accordance with the requirements of section 7308(4), and if a person qualified at the time of the acquisition to serve as an appraiser of the real estate shall certify, in a writing to be preserved among the fiduciary's records, that at the date of the acquisition the unpaid principal amount of the obligation does not exceed four-fifths of the fair value of the real estate.