Ready Made Trains GP Beep...creepy

I'm assembling items for my O27 micro/mini , Carl Ardnt -inspired proto-based short line project and came across several RMT/Ready Made Trains Beep GP9 locomotives at Star Hobby this week. All were in in terra cotta steel-industry base color schemes with one Bethlehem Steel, Sparrows Point lettered...where Dad worked his career and we lived next door for most of my childhood so this was an immediate and VERY exciting purchase. I was informed that these were picked up from the York Show; all appeared new and never run. Cost each...$65.

Test running this little switcher on my carpet test loop, Lionel O27 track and a Williams transformer...this little switcher prototypical crawls at low speed unlike anything I've ever seen outside of contemporary HO and N...and unmodified brass. Switching/short line running involves short trains so I attach 6 Lionel asst cars and the performance remains...around O27 test curves. I've yet to test it on my K-Line switches but this loco is frigging phenomenal. It creeps a bit better than the RMT Bang line, which are no slouches. For kicks I pulled out several MTH switchers costing hundreds more and the $65 RMT Beep out crawled them.

I went back to Star Hobby the next day and bought the remaining 4 in various Steelton and other industry lettering. What the heck is the operating motors and mechanisms in these little gems?