(1) No license shall be required for the use of the following commercial weighing or measuring devices and such devices shall be exempt from testing:
(a) Person weighers also referred to as pennyweight scales;
(b) Any scale used as an in-plant scale to determine ingredients or other such services where the end product or service is determined by some means other than the in-plant scale;
(c) Those scales operated by the United States postal service;
(d) Postal scales used exclusively for determining postage fees and where final determination of weight is made by the United States postal service;
(e) A pharmacist's prescription scale having less than a four-ounce capacity;
(f) Any other device exempted by the commissioner by rule.