...I think it was a mouse-nest or something. I'm unsure since the only thing in there that resembled a mouse-turd was bright-green in color. I figured it was a pick or maybe another bridge pin (I did find the one bridge-pin I dremeled out of it once when the top broke off), but this was off guard (It all came apart as it fell out of the guitar, I guess it was one solid lump inside).
Just goes to show you that you never know what a used guitar may have been through.