J&G Weir Company, 1932-1943
Weir W-1 - Autogyro with two-blade rotor measuring 8.53m in diameter plus a 40hp Douglas Dryad HO-2 engine. First flight May 1933.
Weir W-2 - Derivative of the W-1 as a "jump-start" autogyro with 50hp Weir O-92 flat twin-cylinder engine (according to Apophenia, the engine was also referred to as "Dryad II" in other sources). Used a modified W-1 rotor utilizing the first auto-dynamic rotor head. First flight March 1934. To solve some stability issues, it was later fitted with tail surfaces of the W-3. Planned for production but did not come to fruition.
Weir W-3 - Single-seat experimental "direct take-off" autogyro with inverted 50hp Weir Pixie I 4-cylinder inline engine and clutched two-blade auto-dynamic rotor measuring 5.66m in diameter. First flight July 1936.
Weir W-4 - Refined W-3 design with inverted 68hp Weir Pixie II 4-cylinder inline engine. Built in 1937 but was destroyed during a test when the jump-start caused the aircraft to roll onto its side. The last of Weir autogyro designs.
Weir W-5 - Single-seat twin-rotor helicopter based on the Cierva-licensed Focke-Achgelis Fa 61 design with fan-cooled 50hp Weir Pixie II engine. Thrust was controlled by rotor speed. First flight June 7, 1938.
Weir W-6 - Larger two-seat derivative of the W-5 with fan-cooled 200hp DH Gipsy Six II engine driving twin 3-blade rotors on welded steel tube outriggers. First flight October 27, 1939, but work stopped in mid-1940 due to the outbreak of WWII.
Weir W-7 - Project for a three-seat "gyrodyne" helicopter with 3-blade main rotor and offset torque-countering rotor mounted on the shock-strut of the starboard wheel undercarriage. Unbuilt. Was offered to the Royal Navy as a "Fleet Shadower" ASW aircraft.
Weir W-8 - Project for a single-seat experimental helicopter with blown single-rotor system which Weir called "The Reaction System", comprising of a compressor fitted to either a de Havilland Gipsy Six or Rolls-Royce Kestrel engine. Unsuccessful.
Cierva-Weir (with Cierva Autogiro Company), 1943-1951
The following also fit respectively into Cierva's designation system, however the "W"-prefix was retained.
Weir W-9 - Two-seat single-rotor helicopter with fan thrust countered rotor torque. Based on the Sikorsky R-4/R-5 with the 200hp DH Gipsy Six II of the W-6 (other sources say it was a 205hp DH Gipsy Queen 31). First flight 1946.
Weir W-10 - Project for a four/six-seat helicopter similar to the W-9's basic layout powered by a 510hp Armstrong-Siddeley Cheetah engine.
Weir W-11 "Air-Horse" - Tri-rotor helicopter designed to carry 24 passengers.
Weir W-12 - Project for a smaller derivative of the W.11 powered by RR Dart turbines. Unbuilt.
Weir W-13 - Not used.
Weir/Saunders-Roe W.14 "Skeeter" - Two-seat helicopter. Originally a Cierva-Weir development but was later taken over by Saro per acquisition of the company in January 1951. Production ended in 1960 after Saro became part of Westland. 77 total variants were built.
Great list as usual but the chronology is questionable. :/
See my reply in the Cierva thread.