The letters behind the 580 are the different models. I have a 580D they were made in 1982and1983. Then they started the 580E the next year and so on. I think this years models are 580l. They made some 480 with the same lettering system but the machine was smaller. This machine you are looking at is pretty old. It is probably somewhere in the 50 hp range. My 580D is 55 hp. Mine is not an extend-a-hoe but will dig 12 feet deep. look at the bushings in the backhoe swing clynders and dipper cylinders. If you let go of the handles on the hydraulics and it still swings sloppy, then it is probably pretty well worn out. Construction equipment parts are pretty expensive to buy.