Panzer Art Rgt 89 formed from the former Art Rgt 89 in 1942. As such it was motorised and so I would expect to see (mot) stamped on your tag. With that in mind I think it is a copy.
The '9' in the stammrollen number and the regimental ID appear to be the same font. This is a bad sign in my book.
That is spot on. The "9" is a red flag.