Section 111G. A policy of insurance issued under subdivision (b) of clause sixth of section forty-seven, insuring a person against loss in excess of the amount of any underlying liability insurance may also include his spouse and unmarried dependent children under twenty-three years of age in respect to medical expense which is greater than a stated deductible amount. As used in this section ”a stated deductible amount” shall be the greater of (1) the minimum deductibles shown in the declarations in the policy or (2) the amount of benefits provided for eligible expenses under other medical expense coverage.