The neck has a pleasantly rounded profile that is fairly slim and fast, and the tone is very rich and loud. The spruce top has darkened nicely, and it is very attractive. It is otherwise in good shape with no cracks or repairs and the frets show very little wear. I did a quick cleanup on it, but when I am done with school it will need a more thorough cleaning and fret polish. So, there were little foam bits stuck all over it and piled up inside the body too. This guitar had been sitting for years before I got my mitts on it, and it came with a plastic case with foam that had completely disintegrated. The neck is mahogany with a rosewood overlay and an inlaid logo, and the bridge and fretboard are rosewood too. I am going with laminate until I figure out otherwise. The top is solid spruce, and as I said earlier the back and sides are mahogany, though I cannot tell if it is solid or a laminate. The body has the traditional broad-shouldered shape, and there are 14 frets clear from the body. Maybe it stands for solid wood (top and/or back and sides), or maybe it means that there are scalloped braces, but I am not exactly seeing any in there… The “M” in the model name stands for mahogany side and back, and the “S” is a mystery. The model name is a little easier to figure out, as this is pretty much a copy of the Martin D-18 dreadnaught. The SDM-18 guitar that we are looking at today was built in Korea, though it is hard to get an exact date as the serial numbers seem to have been issued with little rhyme or reason. A German company (AMI Musical Instruments GmbH) bought the name and started selling made in China guitars. Seeking further reductions in labor costs, in 1994 they stated importing instruments from Taiwan, and then Indonesia by the time Martin folded the brand in 2007.

The Sigmas were good guitars, though not wildly successful, and in 1984 production moved to Korea. So, the Sigma brand was their effort to fight back.

This was particularly important to them as around that time many Japanese companies were building guitars that looked just like theirs, and it was hurting their business. Sigma guitars were introduced in 1970 as an attempt by the venerable Marin guitar company to get a toehold into the entry level guitar market by licensing the production of instruments from overseas. This is an early 1990s Sigma SDM-18 6-string dreadnaught. We are going to look at something a little different today - a pretty cool budget acoustic guitar that I picked up at the monthly flea market they have by my house.

Sigma serial numbers guitar