Individual carcasses of poultry meat or packages of cut-up poultry or poultry parts need not be marked with class designation in any of the following cases:
(a)
If they are prepared for use by institutions or public eating houses.
(b)
If they are prepared for use for processing.
(c)
If they are prepared for transportation or being transported to a plant for further preparation or packaging, and packaged in shipping containers which hold several carcasses or packages of such poultry.
Each shipping container shall be clearly and conspicuously marked with the proper designation of class, and of the intended use, in letters at least one-half of an inch in height, on a surface which is readily visible to the purchaser.