Usually a little something in the finish would render it a "second". My friend Mik's dad did the production refinishing for Gibson when they were here in the Zoo and if it was past what he could get right, it got stamped "second" in the wood. One of a few reasons for the designation. An interesting aside, his dad has a big set of shelves with little pieces of exotic wood remnants of all kinds from all over the world - pieces that are 1/4" thick and maybe 2" or 3" x 4". A lot have the names written in pencil on them and many I never heard of.