Hello,

this is an old steampowered excavator manufactured by the Marion Power Shovel Company which also built the NASA Crawler Transporter.
These steam shovels were used in times when there were no hydraulic excavators yet. For example, they were part in the construction of the Hoover Dam together with Mack AP Dump Trucks.
The excavator cab houses a standing boiler and steam engines driving winches pulling ropes or chains to operate the boom, stick and turn the engine housing.
There also were versions mounted on railway cars.
If you were looking for a modern excavator see Excavator.