The JN6 and JN8 models have a serial number inside the driver side glove compartment. 7 digit serial number beginning with a 2 means 1975-1979. Search for the serial number of the brand United Musical Instruments U. Serial numbers seem to change to a 6 digit version at this point. Please feel free to submit your own Yamaha serial number to help me work this out. Even though the R13 was officially introduced in 1955 some versions of it apparently existed beforehand, though 1955 was the official final production design.
If it's in good condition you might get £200-£300 here in the UK. Yamaha trumpet serial number lookup CONN GRAFTON HOLTON KEILWERTH KING LeBlanc MARTIN SELMER SML YAMAHA YANAGISAWA.
