Manufacture or assembly of electrical appliances, electronic instruments or precision devices, radios, phonographs (including the manufacture of parts), musical instruments, toys, novelties, sporting goods, and photographic equipment, only when fully enclosed within a principal building, subject to the following:
(1) The minimum lot size shall be one acre.
(2) The minimum lot width shall be 175 feet.
(3) The minimum setback from any lot line shall be 50 feet.