The F and J model Fairchild F-27's and the FH-227's - RDa 529's and 532's respectively - had a two stop propeller. In addition to the flight fine pitch lock there was a cruise pitch lock that engaged automatically in cruise when the propeller went past 30 or 32 degrees - I forget which and am too lazy to go look up. The lock would remove itself automatically as the aircraft slowed from cruise, but it case it didn't the lock could be removed manually by selecting the HP cock to the full forward Lock Out position. This worked well but if for whatever reason a prop somehow became jammed on the cruise pitch stop it would hang there. A way around that was to punch a feathering button momentarily to drive the prop forward off the lock. I could never figure out why the F-27's had that, another nickname for them being The Flying Blimp, but apparently the two stop prop came about at the request of corporate operators who were leery of a prop fining off toward flight fine at cruise speed. The G159 had them, so it seems to have been a me-too addition by Fairchild. The G1 I can see, it was after all a 290kt airplane.