Final answer:
Uniform clothing that should be marked varies by context; military uniforms require markings for identification by MPs, school uniforms need to be marked for policy adherence, and there is historical significance in marking clothing to delineate class and rank.
Step-by-step explanation:
Regarding regulations and which uniform clothing should be marked, there are various contexts to consider based on the provided references. In a military context, as mentioned, soldiers on leave were required to wear uniforms for identification and regulation purposes. The principle behind this is the easy identification of military personnel by Military Police (MPs). In educational settings, school uniforms often need to be marked for identification to adhere to policies. For school merchandise, one might conduct research, prompted by organizations like USAS (United Students Against Sweatshops), to ensure their school's apparel is made adhering to ethical standards. Historical contexts such as the clothing of the Joseon scholar-officials and the nineteenth-century bourgeoisie highlight how certain clothing marked class identity or rank, illustrating the importance of identifying markers in uniforms across different periods.