Many of you may have spotted the Japanese stamps and/or marks on Japanese Motorcycle parts and other products.

As you all know, the Japanese companies started working very accurately and documented everything in order to make rapid progress. Our main motorcycle parts were also "certified" so to say, with production dates and checking dates as well. Here as example is a crankcase half from my humble Yamaha MF1.

The first date is the production date of the casting: 36.8.24, the second date the checking date of the machined and ready to use for assembly, crankcase half: 36.9.9. In Japan they always start with year,month,date.

Japanese Year stamp or mark

Mr. George Higashiyama, the General Manager of the Yamaha Europe Parts & Accessoried Division, was so kind to send me this "translation" of the second mark.

Japanese Year stamp or mark

So with the "Showa" period year stamp, simply add 25 to find our year so to say!

We concluded that sometimes you can find even 3 marks! Production, Quality Control and Assembly. Please have a look at your old items. Generally these stamps and/or marks were not much used after the mid-1960's.