My godness - an upside-down MAR - Mercury Arc Rectifier in its original wooden casing, forgotten in the shadows of an abandoned industry. Note the ancient supporting straps with rusty springs attached to the casing.

We're talking about an an item that went out of fashion some fify years ago...

Note the pool of metallic mercury in the bottom of the glass bulb - it must be several kilos !! Let's hope nobody breaks it - mercury spill of that magnitude would be a really bad thing