Contact for purchase info.  The additional 2.5inch coil and core are included. Leedskalnin's specifies brass or aluminum for the coils forms, however aluminum produces better results.  This coil is vital to understanding the inner workings of AC and also demonstrates Leedskalnin's light making machine -- his 'best machine'.  He found that the most efficient way to make electricity was with coils moving through a field magnet rather than permanant magnets moving past a coil.  He also claimed to have a patent application on file for a device that was based on this concept.  This device does require an outside power source. 

Custom Perpetual Motion Holders and Leedskalnin's Best Machine

If the concept behind Leedskanin's light making machine was the most efficient, what is the reason for the generator in his workshop? 

It operates on a concept that is less efficient than his best machine.  Perhaps efficency wasn't a concern, but rather frequency.  

It's manual hand crank design makes it possible to pinpoint or resonate with just about any frequency -- a variable frequency AC generator. 
Matt Emery

Suppose you had a wheel and many coils around the wheel turning, then you would. be making all kinds of light. Do not make the machine, I already have the application for patent in the Patent Office. I made ten different machines to make magnetic currents, but I found this combination between field magnets and coils the most efficient.
The Light Machine, Leedskanin's Best Machine
Perpetual Motion Holder Scematics and Leedskalnin's Original Writiings
Dave Nelson's Coral Castle Commentary
What Ed Wanted You To See
Castle Photos
Perpetual Motion Holder
Castle Photos
Ed's Pics
Tips For The Rocket People
Dave Nelson's Commentary on Leedskalnin
Ed's Generator
Leedskalnn's Writings
Magnetic Universe