If you soak the field frame, don't use solvent. Hot water (almost boiling), Dawn dishwashing liquid, and a stiff fiber scrub brush will clean it up nicely, and it won't destroy the insulation on the field coils. Don't even think about removing the fields- - - -those big "screws" need a special clamp assembly called a pole shoe vise to get enough force on the screws to make them move. The tag is attached with rivets in blind holes. A small chisel and a ballpeen hammer will remove them, and I think some of the aftermarket vendors have replacements. I'd leave the tag in place and work around it. Have fun!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!