I have a Sigma DR28H, serial #020781 with cfmartinCo est.in 1970 on the headstock and the made in japan stamped (burned) on the inside bracing. Can anyone give me any info on this. One sight says it was made in 1990 and another sight says between 1980-1984. and also does the H stand for Herringbone? There is also a label on the heel stock with the model and serial #. someone wanted to trade me his Taylor guitar for it but I declined. any info would be appreciated, thanks