number. The remainder of the number is the sequence number for that unit (guitar or bass) within the production run. The format is PPPNNNN where PPP is the production run number and NNN or NNNN is the sequence number within that production run. 3. Hagstrom did keep detailed records for each unit produced, and there is a book to that effect but not widely available. you may want to seek it out. Without the book you may be able to determine the year however. Here are some real-world examples: a. Some serial numbers reveal a clear-cut result. For example, serial number 618324 is from the production run 618 which consisted of 1000 Hagstrom II guitars started and completed in 1964. Therefore, all units with a 618NNNN serial number are from the year 1964. b. However, others are less clear. For example, serial number 680873 is a Viking V-1 and the 873rd guitar made in production run 680. That run started in 1965 and completed in 1966. 1000 units were made in that run, so it is impossible with existing records to know if this guitar was actually made in 1965 or made in 1966. We know that this sequence number (873) is a high number in relation to the total of 1000 guitars produced in the run. We can therefore make the guess that it was most likely produced in 1966. The best that can be said in this instance is that the actual manufacture date is no earlier than 1965 and no later than 1966. 4. Serial numbers were etched on the guitar neck backing plate where the neck is joined to the body. There are instances where the serial number appeared on the input jack plate (seen on a Hagstrom Swede from 1973)as well. This may have been common and an alternative serial number location. 5. In 1975/76 the numbers “53” were added as a prefix to the serial number (53 PPPNNNN) and should be ignored for decoding purposes. 6. Production run numbers are in general sequential with some exceptions. In a real-world example: Production runs 706, 707, 708, 709, 711, 712, 713, 714, 715, 716, and 718 are verified to have all started in 1967. It can then be predicted that runs 710 and 717 also started in 1967, if those runs occurred. The likelihood of the start date being consistent relative to those adjacent to it