The First Edition of Age of Steam can be distinguished from the Second Edition in three major ways. First, on the First Edition board, "Detroit" is misprinted with a "1" instead of a "3". Second, the Income Track on the First Edition does not wrap correctly to 50, and the income reduction is not listed as "-10" when at or above 50. Finally, Second Edition rules include rules revisions and additions not included in the First edition rules.

Source: http://boardgamegeek.com/article/2523578#2523578