The SJ (SOUTHERNER JUMBO) was made between 1942 and 1978. The Southener Jumbo was a spruce topped acoustic jumbo guitar with mahogany neck, sides and back. Out of necessity the wartime models sometimes used different materials, some of the early ones had rosewood sides and back, and some examples have maple sides. It came in a sunburst finish, but a natural finish option was introduced in 1955 (known originally as the Country-Western Jumbo and later the SJN - Super Jumbo Natural).
There have been minor changes over time with this model, the earliest ones had a banner inlay on the headstock until 1946, when it was replaced by a pearl banner logo. From 1962 to 1970 adjustable bridge saddles were used. In 1974 the body and neck binding was changed. The older ones are much more valuable, comanding ten times the price of the seventies examples.
Source: Blue Book of Acoustic Guitars 9th Edition. Z.R. Fjestad