What you have is definitely an espresso maker. That particular style was invented in the 1930's by Alfonso Bialetti. The original had 6 sides rather than 8.
I'm glad you got it to work -- but the fundamental difference between this device and a percolator is that this one uses steam as pointed out by <b>newtx</b>. A percolator just uses hot water that recirculates through the grounds. The flavors are disinctly different and if you like what you get using what you use then who cares?
For a really, really good cup of coffee try one of these:
http://www.sweetmarias.com/prod.brewers.vacuum.shtml
Doug