Iver Johnson Revolver Serial Number Database: Best

Serial numbers generally parallel the exposed-hammer models but with an “H” prefix or suffix for some years—though often no prefix. Use same ranges cautiously.

These are the most reliable, though incomplete, resources: Iver Johnson Revolver Serial Number Database BEST

Without the book, you can identify the general era of an Iver Johnson revolver by looking at the serialization format, particularly for the famous "Safety Automatic" revolvers. resources: Without the book