Are you trying to find the value of a specific piece, or are you just looking to verify if it's safe to ?
If you cannot find your specific number, the following forums have experts who own the Goforth book and can provide an exact year: Iver Johnson Revolver Serial Number Database BEST
Unlike modern firearms, Iver Johnson numbers are often hidden. To find the true serial number (which often includes a vital letter prefix), check these locations: Are you trying to find the value of