Just a quick one..

What's the difference, between a Sigma Martin, and a Martin?
The first one, Sigmas were made in Japan.
Martins are made in PA, USA.

Sigmas were imported as and entry level guitar for Martin. Kind of like Squier is for Fender and Epi for Gibson.
--- Joe ---
77 Bradley LPC || 07 PRS CE22 || 11 PRS MC58 Artist || 95/02 Fender Strat || 99 Gibson LP DC Std Lite
06 Ovation Elite-T || 12 Martin GPCPA4
Boss GT100 || Peavey Stereo Chorus 400 || Peavey Bandit 75 || Roland JC77
Exactly. They are not bad, generally... After all, Martin had it's name to defend and didn't want to sell a junk product.
I had a friend who had one for years and it sounded just fine.
My uncle just found one two months ago at a thrift store for sixty bucks and it plays amazingly well...