[drcy]

A premium is something you send away for for a price (whether monetary payment, box topic, coupons, other), while a supplement is something extra included with the main item. Collectors sent away with payment for the Baseball Magazine premiums, while the Police Gazette Supplements were included in the magazine. When you don't know how a print was distributed/obtained you won't know whether it was a premium or a supplement-- and there are numerous cases in the hobby of this.

Baseball cards is an interesting area in that how an item was distributed is an essential part to the item's identity. By standard definition, a baseball card has to have been distributed commercially in some way or form to the general public, and cards are categorized and often valuated by how they were distributed (premiums, supplements, inserts, trade cards, other). That's why baseball card collectors spend so much time pondering and discussing how items were distributed.