Create a Legal Notice & Send via Fastmail or Registered Mail
It seems that the words post office,registered mail,certified mail,priority mail express,and signature confirmation are trade marked. : r/mildlyinteresting
Kuwait Ganzsache Einschreibe Umschlag 40 c Segelschiff Registered Letter Ganzsache postal stationery | MA-Shops
Australia - 24+25 C. QEII registered letter stationeries both unused - Postgeschichte Kemser
How to Send a Registered Letter: 11 Steps (with Pictures)