You will often see listings for the "Korg M1 EX." This is not a different serial number range.
The M1’s enduring popularity has led to a small but real market for counterfeit parts and "franken-synths"—units assembled from the broken shells of multiple M1s. A missing, damaged, or mismatched serial number sticker (e.g., the sticker says "Made in Japan" but the serial format is Italian) is a major red flag. Moreover, if you are buying a used M1, always record the serial number. If the instrument is ever stolen, that number is your only proof of ownership. Korg M1 Serial Number
For Korg equipment from this era, you can often estimate the age by the first few digits: The Korg M1 Plugin Tutorial: An Overview of the M1 You will often see listings for the "Korg M1 EX
Crucially, the prefix numbers are the most significant digits. For the vast majority of M1s, the first digit or first two digits indicate the year of manufacture, while the subsequent digits represent the unit’s sequential production number for that year. Moreover, if you are buying a used M1,
Some users report that holding [ENTER] + [9] while powering on may display the OS version and sometimes an internal date, though this is often the software build date rather than the hardware's birth date. Why Dating Matters
