I've been offered a Martin mandolin, an A model with F holes (teardrop), it has good maple flaming on the back, sides & neck, as well as the back of the headstock. The markings inside the mandolin are 2-15 (the "2" is hard to be sure about, it could be something else) but the 15 is clear. Below that is a number 18265. What do the numbers mean? Also, as an owner of several Martin guitars, I recognize that Martin was better at guitars than mandolins, but are these older Martins good sounding instruments. I'm just learning to play. Thanks!