No person shall keep for the purpose of sale, offer or expose for sale or sell any sewing, basting, mending, darning, crochet, tatting, handknitting or embroidery thread, put up or packaged in advance of sale on spools, tubes, cones or bobbins or in balls, skeins or other similar forms, hereinafter referred to as units, for either wholesale or retail sale, unless each of such units is definitely, plainly and conspicuously marked to show the net weight in terms of avoirdupois pounds and ounces or the length in yards of such thread, subject to the provisions of this section. When the net weight of such thread, in or on any such unit, is less than two avoirdupois ounces, such unit shall be marked to show the length of such thread in yards as unwound from the unit. Ready-wound bobbins which are not sold separately shall not be required to be individually marked, but the package containing such bobbins shall be marked to show the number of bobbins contained therein and the net weight or measure of the thread on each bobbin. Any two or more similar individual units of thread, sold only for household use and not sold separately, which are contained in a single package shall not be required to be individually marked but such package shall be marked to show the number of individual units in such package and the net weight or measure of the thread in each individual unit, unless such individual units are separately marked. The markings required by this section shall, in all cases, be in combination with the name and place of business of the manufacturer or distributor of the thread, or with a trademark, symbol, brand or other mark which positively identifies such manufacturer or distributor and which shall be filed with the Commissioner of Weights and Measures. The net content of any such unit of thread shall be determined by ascertaining the average net weight or yardage of not less than ten units of thread of the same type and of the same kind of unit, selected at random from such units kept for the purpose of sale, sold, exposed or offered for sale. Such average net weight or yardage shall not be more than three per cent less than the weight or yardage marked on such units or the package containing such units. Regulations for the enforcement of the provisions of this section shall be issued by the Commissioner of Weights and Measures. The provisions of this section shall not apply to wool or to textile products made in whole or in part of wool. Any person who, by himself, his employee or agent, or as the employee or agent of another, violates any of the provisions of this section shall be subject to the penalties provided for in § 43-9.