It's the shovel bucket from a dragline, used in Florida to mine phosphate. It's hard to tell from this picture, but this shovel is really big. You could walk around in there. Draglines and shovels like this were a tremendous step forward in efficiency compared to the handheld shovels and wheelbarrows used when phosphate rock was discovered in Florida in the 1880s. At first, miners dug for river-pebble phosphate, but draglines let them pull off the oveburden and get to buried phosphate rock deposits more easily.
Florida phosphate is a major source of fertilizer for the nation and the world, and has been economically important to the state for over 100 years. Downsides to mining are primarily environmental, from the actual soil removal to energy and water use, to the slightly radioactive by-products stored in mountainous gypsum stacks. Most of Florida's phosphate comes from the Central Florida Phosphate District or Bone Valley, where the corners of Hillsborough, Polk, Manatee, and Hardee counties meet.
This particular shovel can be found to the side of MOSI in Tampa. Yes, that's a red dinosaur in the background.
More Reading about Phosphate in Florida:
Florida Mine Map (pdf)