Nothing, the # on the back of a Baseball card is the card # in the baseball card set. Ex. My baseball card has the # 278 on the back of it. So my card is the 278th card in the set.

it costs 2 dollars

The 1956 Topps baseball card set consisted of 340 baseball cards that measure 2-5/8" by 3-3/4" The following year in 1957 the Topps baseball card measured 2-1/2" by 3-1/2" These cards are smaller than the Topps baseball cards made from 1952- 1956, and are the size of the baseball cards made today. Most modern sports cards measure 2 1/2 by 3 1/2 inches and is referred to as "Standard Size".

Yes.

2$ - 5$