Dug out of an old barn, rusty metal base is 11x7x8, with the plastic dome 14 inches tall. I haven't been able to open it up yet, but there's a hinge on the back so I should be able to. The plastic dome is over some strange electrical bits, including a clockwork spring that moves every time I move the thing around.

Lots of gizmosity in that gadget.

An uneducated guess that it's an igniton for a Model T.   The kind of coil that just sparks continuously when on.  If correct it would be a great ignition for a tennis ball blaster.

well since it was on farm it might be a fence shocker?

Yup, I think it's a very old electric fence controller, possibly made by Esco. I found this pic from a Farm Sale and there it is among a bunch of others.

Updated info, it is a model #4305 made by Electro-Line (just found one on eBay) 

I'm glad you all got it figured out because I was going to guess that it was a road construction marker with that amber colored plastic top. I thought it might have housed a lamp that could be lit at night as a modern replacement to the kerosene pots the used to put out.

It looks like part of Robbie the robots head. Makes me think of Anne Francis.

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