Hereafter every individual or copartnership, who shall engage in the business of manufacturing or vending nostrums or patent medicines, of whatever class or character, shall, for the purpose of taxation, be deemed and taken to be dealers in merchandise, and shall be classed and rated for a yearly license in the same manner, except as is hereinafter provided, as other dealers in merchandise are now by law classed and rated: Provided, That nothing herein contained shall be so construed as to exempt any manufacturer of nostrums or patent medicines from the payment of the proper license fee, or any part thereof, on the grounds that he is selling goods of his own manufacture, from the place where the same were manufactured.