Like D&D, Mutants and Masterminds has gone through a couple editions. Can you tell which one the book you have is? The easiest way is probably to look at the skill list on the character sheet and/or check the publication date.
- Balance, Demolitions, Forgery, Hide, Innuendo, Jump, Listen, Move Silently, Open Lock, Read Lips, Repair, Science, Spot, and Taunt are only found in 1e. The edition was published in 2002.
- Notice is (I think?) the only skill unique to 2e. The edition was published in 2005.
- Athletics, Close Combat, Deception, Expertise, Insight, Perception, Persuasion, Ranged Combat, Technology, and Vehicles are only found in 3e. The edition was published under the name "DC Adventures" in 2010, and as Mutants and Masterminds in 2011.