Hi. I’ve got a similar guitar with the serial number suggesting it would be a 1980. Mines a six string though, and I’m trying to find out the value. The model number appears to be EF 391-ME. It came with the 4 band EQ and the same under the bridge pickup and end pin. Does anyone know where I can check the value on the web? Thanx. : Yes its a 1981, 1st number and 4th or 5th number in the serial number, i forget but i do believe you go by the 1st and 5th numbers. Trevor : : I have a Takamine F400 & I am trying to determine the age. The serial number is 81121104. My guess is 1981. It also has a pickup under the bridge that out puts through the end pin. I think it is a Shadow Transducer. It is designed exactly like a Martin.