With a unique Styrofoam diaphragm, this unit bore the name Natural Sound Speaker (NS Speaker) and was the origin of the "natural sound" slogan Yamaha has continued to use ever since.The front of the NS speaker mounted fully on the rear side of the cabinet (the back of the unit) was also substantially open state, full range driven, and by mounting the two-way consisting of a 30cm (NS-30) or 20cm (NS-20) "squawker" and 5cm tweeter on the front side it had the configuration of a sound field type speaker, actively taking advantage of the effects of reflected sound. The final four numbers are the unit number; 0013 (13).
213=unit number; and that last letter is an internal code. (That first letter is an “oh” not a zero.) The first letter is the year; O=1998. The three numbers are the unit number; this started over each month at 500, so unit number 21. Yamaha Music Craft, Made in Japan, 1999: Letter-letter-###, like so: PM222. The first two letters are the year; Q=0 and I=2, so 2002.
Custom Shop, Made in Japan, 1997-2003: Letter-letter-###, like so: NK333.
The letter at the beginning represents the month, so J would be March (see chart above). Custom Shop, Made in Japan, 1991-1996: Letter-letter-###-letter, like so: HP213J. 111 is the unit number; and the final letter is an internal code. During 1999, they starting the count each month at 200 rather than 500. Tenryu/Wada Factory, Made in Japan, 1946-1968: #####.
The number following the letter is the year, in this case . Using the charts, we see that H=1991 and P=September. Custom Shop, Made in Japan, 2004-: Letter-letter-letter-###-letter, like so: QLY111C. Yamaha Music Craft, Made in Japan, 1997-1999: Letter-letter-###-letter, like so: ON521J. (See previous entry for Yamaha Music Craft for more on the numbering.) Yamaha Music Craft, Made in Japan, 2001-: Letter-letter-letter-###-letter, like so: QIL123A.
Kaohsiung Factory, Made in Taiwan, 1971-2001: ########.
The second and third numbers are the month; 09=September. The first two numbers indicate the day of the month. The last three numbers represent order of production on the day the guitar was made. ” To you folks, we offer the following: Several other serial number configurations used by Yamaha over the years. Having interrupted the launch of new Hi Fi products from the late 1950s to the 1960s in order to focus its development resources on the revolutionary new Electone electronic organ, in 1967 Yamaha began its history as a Hi Fi speaker manufacturer by repurposing and improving the Electone’s NS (Natural Sound) Speaker for Hi Fi audio use.Released in 1974 and featuring the world’s first pure beryllium diaphragm, the NS-1000/1000M won worldwide acclaim for its clear and open sound, and after that models such as the NS-451 and NS-10M, producing good quality sound at a reasonable price thanks to the unique sheet method of manufacturing.Example: hm02316 = the 316th unit made on June 2 of 1961, 1971, 1981, 1991, or 2001. If you still can’t figure it out, please see Yamaha contact info at the bottom of this page. Tenryu/Wada Factory, Made in Japan, 1969-1984: ######.