It could He’s someone at the IRS. But that isn’t necessarily the only explanation.
It is stamped “client copy” so it is likely it either came from Trump’s office or from his accounting firm. It is unsigned. FWIW, we always got 2 sets from our CPA, one to sign and mail and one stamped “client copy” for the files. At least, back in 2005 era. Now, it comes electronically.