These bricks are from radiation detection equipment.  They Interlock to construct a lead wall in portal monitors.

(see photo to show the interlocking edge)

11 11/16″ X 4 1/8″ X 1″ in size and weight  18 lbs. 3.4 oz.

These were free released from a nuclear station. They were used to shield a gamma personel monitor. These should be clean. We of course offer a 30 day return policy if they are not clean enough.
We have a forklift to assist with loading.