You have been indeed very lucky. And I can't find any excuse for anybody throwing away a 060 accelerator board, let alone an A4000T >-(. Have you alredy checked if it works?
Varthall
Makes you wonder how many sought after Amigas and expansion boards have been sent to the dump by people who didn't know any better. I see beige box PCs on the curbside all the time around here. To the untrained eye, the Amiga is just another beige box taking up room in their already over crowded garages. It just shows you the extremes of this marketplace. Somewhere in the world somebody is paying a ton of money for an 060 accelerator and somewhere else in the world somebody is throwing it away in the trash.