Soeren or "danserinden",

I assume You are danish and bought Your Sigmas in Denmark, which might explain why Your instruments are marked "imported and guaranteed by Levin". Levin was after they were bought by Martin, the distributor of Sigmas in Scandinavia, and possibly also in the rest of Europe. At the takeover, Levin had already started their own import of japanese guitars, sold under the brandname "Nippon Best".

They were laminated wood in top and bottom, presumably of fairly good quality, Levin would never have put their logo on them otherwise.

In the 1975 Levin catalog, these guitars were still in the Levin catalogs, but I do beleive these guitars were later sold under the Sigma name, and that You have one of these.

In the 1975 catalog there is a Nippon SG-2, and I am shure I have seen a Sigma SG-9 on internet with the same shape of the headstock, quite differrent from the typical Sigma/Martin shape. The SG-9 i saw, if I remember correctly, was black, with double pickguards and a bit decorated.

link to 1975 Levin catalog:

http://goyaguitars.tripod.com/levin75_8.htm