HSN Code 3504 refers to "Peptones and their derivatives; other protein substances and their derivatives, n.e.s.; hide powder, whether or not chromed (excluding organic or inorganic compounds of mercury whether or not chemically defined)." This classification code is essential for identifying protein substances and related items for import/export purposes based on their nature, composition, and intended use. Common products under HSN Code 3504 include peptones, protein hydrolysates, collagen, and hide powder. Additionally, the GST rate for peptones and other protein substances under this code ensures accurate trade compliance.