[R Leonard]

As George noted -

From United States Naval Aviation 1910–1995

1931
22 January The Navy ordered its first rotary winged aircraft, the XOP-1 autogiro, from Pitcairn Aircraft, Incorporated. (Page 79)

1931
23 September Lieutenant Alfred M. Pride piloted the Navy’s first rotary wing aircraft, an XOP-1 autogiro, in landings and takeoffs aboard Langley while underway. (Page 81)

1935
12 March The Navy issued a contract to Pitcairn Autogiro Company to remove the fixed wings from the XOP-1, thereby converting it to the XOP-2 which thus became the Navy’s first heavier-than-air aircraft without fixed wings. (Page 89)

According to bureau numbers listed in the appendix, the XOP-1 was Bureau Number A-8850. Two additional XOP-1s were A-8976 and A-8977.