Interest on property withheld by representative of decedent‘s estate.) At the expiration of a period of 2 years after the issuance of letters of office in a decedent’s estate, the representative shall be charged with interest at the rate of 10% per year on the fair market value of all the personal estate which has come into his possession or control and has not been properly paid out or distributed, except for good cause shown. The interest shall run from 2 years after the issuance of letters or if personal estate comes into his possession or control subsequent to 2 years after the issuance of letters, interest on the subsequently acquired personal estate runs from 6 months after such personal estate comes into his possession or control, except for good cause shown.