Fokker G.I
Sorry @Bordkanone 75, but I'd already prepared this before you posted yours
The G.I was a Dutch heavy fighter designed immediately before WWII. Of typical pre-war Fokker mixed construction, it featured a metalised crew capsule and wooden wings. The first prototype flew in 1937 with Hispano-Suiza engines. It received good foreign interest, and several countries sent crews to test fly the aircraft. On one such flight the prototype suffered a major engine failure that almost led to the loss of the aircraft. Subsequently the engine type was changed to Pratt & Whitney Wasp Junior.
The Dutch military had more interest in a revised version 3-seat ground attack version with Bristol Mercury engines, rather than the 2-seat fighter with Wasp engines, and so Fokker reworked the design for domestic use, while continuing to market the fighter internationally. Interestingly Fokker never used a G.IA/G.IB designation, the factory only ever referred to the aircraft models by their engine types Wasp/Mercury.
The first aircraft were built for Spain and painted in all over Spanish green. The Dutch government impounded the aircraft and prevented their export. Finland also attempted to order the aircraft, and an attempt was made to move the Spanish aircraft to Finland before clandestinely shipping them to Spain, but that was also halted.
Sweden and Denmark also had firm orders, with license production planned for Denmark - all halted by WWII.
As war loomed the Spanish aircraft were impressed into the Dutch Air Force, but not all aircraft were armed or even fitted with radios as the Luftwaffe attacked.
After the invasion the surviving flyable aircraft were taken over by the Luftwaffe.
The larger, heavier Mercury engined version was also starting production at the start of the war. Fokker conducted testing on the Mercury aircraft for modifications planned for the smaller Wasp aircraft. The Swedes wanted a dive bomber, and so dive-brakes were tested on one aircraft. Also the potential of an observer's station for the Swedes in a large belly "bathtub" fairing was trailed and found unnecessary.
Like their smaller siblings some Mercury aircraft were taken to Germany to be used as trainers.
A follow-on version of all-metal construction was being designed as Germany invaded, but the design was not advanced.