Fake or rare?

Sold on E-Bay.
Movement Cal.21.29 with Up/Down Indicator.
On the movement and dial write "BU.AERO.U.S.NAVY".
Start/stop slider.

Found on the Internet a few links with the mention on these watches.

rare,and looks right to me,they are a beautiful watch,top drawer by any measure!!!

Very similar to mine, only without the caseback markings... Longines Master