Many years ago radium-226 and radon-222 sources were used as gamma-ray sources for industrial radiography: for instance a radon-222 source was used to examine the mechanisms inside an unexploded V-1 flying bomb, while some of the early Bathyspheres could be examined using radium-226 to check for cracks.
The last survivor, Ready, was used in support of William Beebe's expedition in his bathysphere in 1930 near Bermuda.