If they are fused on their faces, i.e. with the connection pins on their opposite sides, it may be a combination of a viewing storage tube with a TV camera tube, which could have been used for conversion between different TV standards, e.g. American <=> European.
I believe it's fused on the pin side >=<. I will double check and thanks for the idea. I'm about to start documenting all of the artifacts I have purchased over the past (gulp) 25+ years.
