Any personal property or securities lawfully acquired by an insurer which it could not otherwise have invested in or loaned its funds upon at the time of the acquisition shall be disposed of within three years from date of acquisition unless within that period the security has attained to the standard of eligibility. However, any security or personal property acquired under any agreement of bulk reinsurance, merger, or consolidation may be retained for a longer period if so provided in the plan for the reinsurance, merger, or consolidation as approved by the Commissioner under Chapter 14 of this title. Upon application by the insurer and proof that forced sale of any of the property or security would materially injure the interests of the insurer, the Commissioner may extend the disposal period for an additional reasonable time.