Mich. Comp. Laws § 289.8109

Sec. 8109. All products that are sold or otherwise distributed from a manufacturing, processing, packing, or repacking activity shall be marked with a meaningful, visible, and legible code to enable positive lot identification and to facilitate, where necessary, the segregation of specific lots that may have become contaminated or are otherwise unfit for their intended use. Invisible coding is not considered meaningful coding. The coding format shall be provided to the department upon request. Coding records shall be retained for a period of time that exceeds the shelf life of the product or for 2 years, whichever is shorter.