All of the Sigma's with the Greek sideways M were made in Japan. They changed to the new headstock logo in 1980, but the guitars were still made in Japan through 1984, at which time they switched to having them made in Korea. Your guitar with that low of a serial number is probably very early 1970's. Serial numbers on Sigma's are confusing, but that is a very low number. According to what they sell for on E-bay, if it is in really good shape, it should be worth
$300 to $500. The early Japanese DR-7's are worth more than later ones and seem to have really good tone.