Flaminpyro wins ..... it's an "electric eye" flame detector for gas/oil burners ..... there are two electrodes in a glass gas chamber (like a gas discharge lamp) that become "triggered" (ionized) only from the wavelenghts included between 190 and 270nm, causing a current flow through it, but is insensitive to any other light, so it detect the UV part in this range that is normally emitted from the flame of oil and gas burners, but not the light from, as example, external lights, daylight, incandescent firebricks or burner parts, and so on.
@FP: your item is a complete item itself ? (i'm asking cause the bottom looks as if it had to be hooked somewhere, with that circle of steps) .....
About the images, i think ped means to attach them directly in the forum (going "advanced" in posting, then using "manage attachments" and loading them as attachments for the post, instead to use the quick reply form)