C.R.S. § 35-14-126

(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.