Brass Tag Removal

I use needle nose vise grips to grab the head and then kind of turn them counterclockwise as I pull since they have a sort of spiral like a screw. If that doesn't work if you don't want to damage the tag you have to use a small drill and drill out the head. Those brass tags are pretty cool. I wouldnt want to damage them.

A trick I learned years ago is to use a strip or block of aluminum and drill a hole the diameter of the head of the "rivet". Place the drilled hole over the head of the rivet before drilling the head out so the drill bit does not wander off and scar the plate. Make sure you hold the block securely and drill carefully until you have drilled out the head and not through the plate.
Of course if you can grab the rivet with a vice grip and can remove it that is the easiest but that rarely worked for me.

Never drilled one out on a Cat but drilled many of the green ones. Some of the "threaded" ones came right out using a left handed drill bit.

Good luck

I've made a simple punch out of a piece of 4140HT round stock about 1 1/2" dia laying around. Put it in my lathe and faced the bar down to the center leaving a small tip about 3/32" diameter and 1/8" protruding. Then I looked for the rivets on the inside of the sheet metal and then ground the rivet points flush with sheet metal. Heated the metal around the rivet point some to define where they were and placed my punch on the point and hit it to drive the rivet out. Reason for the short punch is it won't bend when you strike it and the extra weight of my bar stock acts like a bucking bar. If you get the rivet moving then use a regular 3/32"punch or you may get it out enough to grab it with a pair of Vice Grip pliers.
In my attempts; Drilling is very tedious and most of the time the rivet work hardens and you can't drill it especially with a hand drill.
Castings are another animal. I like D4jim's idea with the Left Hand helix drill bit and guide block to unscrew those drive rivets.

The seat  is just sheet metal so you can go on the inside bend them straight or grind them off and punch out the other ones yes you would need to drill out

as for cleaning up the tags a 3m surface conditioning wheel or belt works well or a scotchbrite and some autosol or brasso. the secret to a good shine is two rags one to apply one to buff.