I read this post a while ago, but was left speechless at the time.
Now, I must say CONGRATULATIONS!!! Thank you for the details on the signal. The negative numbers were probably from some iron junk close by, or maybe your ground balance being off; making it sound iffy. You should air test it to see what it rings up at without any ground interference.
Clean that baby up a little! Distilled water and a soft bristle brush can't hurt it. Pat dry with a soft cotton cloth.