An insurer may invest in nonassessable, except as to bank or trust company stocks, and except for taxes, common stocks, other than insurance stocks, of any solvent corporation organized and existing under the laws of the United States or Canada, or of any state or province thereof, if such corporation has had net earnings available for dividends on such stock in at least 5 of the 7 fiscal years next preceding acquisition by the insurer. If the issuing corporation has not been in legal existence for the whole of such 7 fiscal years but was formed as a consolidation or merger of 2 or more businesses of which at least one was in operation on a date 7 years prior to the investment, eligibility of its common stock under this section shall be based upon consolidated pro-forma statements of the predecessor or constituent institutions.   [PL 1969, c. 132, §1 (NEW).]