When selecting metal calendars, the choice of base metal determines durability and perceived value. Aluminum is popular for its lightweight and rust-resistant properties, while Stainless Steel offers a premium, heavy feel suitable for high-end corporate gifts. For the finish, ensure the supplier uses Anodizing or Powder Coating to prevent oxidation and fingerprints. If the calendar features moving parts (perpetual style), verify that the surface hardness is sufficient to resist scratching during daily adjustments.