The "Made in Japan" stamp is highly sought after. Many players believe the Japanese quality control is superior, particularly for the "Handmade" professional series (300 series and up).
Determining a Yamaha flute's age often depends on identifying the era of production and specific design changes, with early models featuring "Nippon Gakki" marking, moving through "S" and "SII" series in the 1980s and 90s to modern numerical naming conventions. Yamaha Flute Serial Number Chart - Facebook Yamaha Flute Serial Number Chart
Let’s say you have a YFL-321 (intermediate, silver headjoint). The serial number is 890,123. The "Made in Japan" stamp is highly sought after