Is this illegal?

Not illegal in Australia....

And if it didn't have the chrysler corporation wording it is just a piece of metal with numbers...
And you can legally buy a decal with that wording.so really what's the big deal...if your tag is lost or damaged...just get a new one...the only country that carries on about it is the usa....overseas couldn't care less
Here in Oz it's the stamped numbers on the shell authorities are concerned with not a piece of tin that is riveted on