Accepted by the US Pat. Off., perhaps, 4 letters
Govt.-certified, 4 letters
Govt.-certified, as a patent, 4 letters
Kind of mail: Abbr., 4 letters
Like a pat. no longer pend., 4 letters
Like many a TM, 4 letters
Officially listed: Abbr., 4 letters
Recorded, as a patent (abbr.), 4 letters
Trademark abbr., 4 letters