Shot peened cast alimunum more than likely. Or cast iron to hold up to the higher rpms/pressure/turbocharging.

As far as I can figure, he plays an Epiphone EJ-200. There are a few models, but I think he's playing the one at the 400$ price point. There are lower end models, but still, under 500 for a great sounding guitar is pretty awesome! Look for the "crown" style fret inlays. They start to get a bit more expensive when looking for the acoustic/electric though. Cheers!

I think you are referring to a method of locating a nut in a piece of sheet metal.

A rivet head nut is a nut with has a small projection not much thicker than the sheet metal to which you intend to fit it.

This projection fits through a pre made hole in the sheet metal, and the small projection is peened over (deformed by hammering) to fix the nut to the sheet.

galvanized piping is acceptable but not necessary. all steel piping must be wrapped when entering ground at least 6" (a foot is better) bushings are not allowed unless properly peened so its better to just use bell reducers. and finally be sure to size your pipe according to the BTU requirement of the appliance being serviced

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 2 words with the pattern PEEN--. That is, six letter words with 1st letter P and 2nd letter E and 3rd letter E and 4th letter N. In alphabetical order, they are:

peened

peenge