A license tax for revenue purposes only is imposed on amusement devices. The tax shall be in the annual sum of fifty dollars ($50.00) on each amusement device displayed or operated within the city; provided, however, if any business shall have on display more than five but less than sixteen (16) such amusement devices, the amusement tax shall be the sum of two hundred fifty dollars ($250.00). If any business shall have on display sixteen (16) or more such devices, the tax shall be in the annual sum of two hundred fifty dollars ($250.00) plus twenty-five dollars ($25.00) for each such device over fifteen (15) in number. If an amusement device is first displayed or operated after the commencement of the calendar year, the amount of the tax on such device shall be reduced by one-twelfth for each month of the calendar year which shall have expired prior to the date the amusement device was first displayed or operated. (Prior code § 8.105)