Dating my sigma guitar Camliveultimate
In a vast majority of cases, the serial number on a Martin guitar can be found inside the body near the neck joint.
During this time period, they actually had "Sigma Guitars by Martin & Co." on the headstock. The DR1ST was modeled after the Martin D-16 from what I could find.
Numbers 900001 to 902908 were used by a short run of Sigma-made Martin models in the early '80s so don't not appear on Martin models.
Every guitarist has that one special guitar that they wished they had back.
So you need to figure out the date of your Martin guitar. Unlike the nebulous web of varying schemes and numbering systems used by companies like Gibson over the decades, Martin has employed a single string of serial numbers for a vast majority of its guitars going all the way back to 1898.
This means that just using the serial number of your Martin will give a very accurate date of when the guitar left the line.
I don't know anything about these guitars except they were made by/for Martin, I think in Korea.