Section 21. Whoever knowingly causes to be printed or published a false or fraudulent notice or advertisement for help or for obtaining work or employment, or whoever, in an advertisement for help, if the person to be employed is required to purchase a particular article of value as a condition of his employment, fails to state that the offer of employment is contingent upon the purchase of such article and the purchase price of such article, shall be punished by a fine of not more than two thousand dollars or by imprisonment for not more than three months, or both.