Your device may or may not have the legs attached. Mine did not as it was likely rack mounted before. So in this case I only have two screws to remove.

Clearly the body of this device has seen better days. That being said it still runs like a champ. Oddly it has the word Apache written on the top-side. I wonder if it was used at some point to service Apache Helicopters.

Now the case should slide right off.