Martin Mull, between songs on his album 'Martin Mull and his Fabulous furniture in your Living Room' (1973), drew attention to his scarf? tie? and said that in the little Portugese village where it was made, a deliberate mistake was woven in as 'only God is perfect'.

Oh, and a friend of mine has a Martin D28, and I noticed that, viewed from the front, the strings on the left-hand side were thicker than the strings on the right! Same principle, surely!