I did a google search but did not find much info except for below:
http://forsale-l.amateur-radio-society.com/RadioGear/Analyzers/Ge-amplified-s
peaker-4EZ18A13/
LBI 4225 GE maint. manual vehicular charger model 4EP75A10 (option 5413) &
speaker-amplifier model 4EZ18A13 (option 5422)
"General Electric amplified speaker. Model 4EZ18A13, operating from 12 VDC.
This speaker amplifies the low power audio, from vehicular mounted portable
products. It provides 5-10 watts of power. Great for hand held 's, mobile
radio's, scanner's etc. Tired of turning your volume up so high, with the
distorted audio, while in motion? Now you can have clean undistorted higher
power audio! The amplified speaker comes with mounting bracket and 5 pin
connector. Simply apply external audio, and 12VDC! Simple installation and
operation. This item is in very good condition. It may be brand new, listed
as used, a long storage item."
It doesn't look too complicated. If the 5 pin connector is still attached chop it
off, take it apart and trace the wires.
........good luck