It shall be unlawful for any agent of a fire insurance company, or of any other insurance company which is required to have its policies signed by a resident agent, to sign any blank policy of insurance. Upon satisfactory proof that any agent has violated the provisions of this section, the commissioner shall revoke such agent's license for all companies for not less than three (3) nor more than six (6) months for the first offense, and for one (1) year for the second offense.