The original prototype of the GL-810 designated L 2-01 was built at the Saint-Maur works of Gourdou-Leseurre near Paris, and was flown for the first time at Sartrouville in the summer of 1926. Powered by a 380 hp Gnome-Rhone Jupiter radial air-cooled engine, the L 2-01 was a two-seater of mixed construction, the fuselage being a steel-tube structure covered by light alloy panels forward and fabric aft and the wings being fabric-covered wooden structures. The soundness of the floatplane's structure was demonstrated when, during official trials at Saint Raphael in 1927, an engine failure necessitated a forced landing in a sea of strength 6 without any damage resulting.
Six pre-production aircraft were ordered under the designation L 3, these differing from the prototype in being three-seaters powered by the 420 hp Gnome-Rhone 9Ady Jupiter nine-cylinder air-cooled radial engine, and in having the wooden wing spars replaced by steel spars. Catapult trials were undertaken at Saint-Nazaire in August 1929, and orders were placed for twenty-four production machines under the designation GL-810.
The GL-810 differed from the L 3 in having the floats lengthened by 27.5 in (0.70 m), and armament consisted of one fixed forward-firing 0.303 in (7.7 mm) Vickers machinegun and two 0.303 in (7.7 mm) Lewis guns on flexible mount, plus two 165 lb (75 kg) G2 bombs.
The airframes were manufactured at Saint-Maur and the floats were produced at Les Mureaux where the aircraft were assembled. Twenty additional GL-810s were ordered on September 2, 1931, seventeen more aircraft being added to this contract on March 31, 1932. A week later, ten more aircraft were ordered, and a final contract calling for fifteen machines was placed on October 5, 1933, to bring total production to 86 machines. Some of these were designated GL-811, this version differing from the standard GL-810 in having folding wings, and the final machines were designated GL-812, these having the folding outboard wing panels staggered by 4 in (0.71 m).
In July 1931, Escadrille 7S2 was formed with GL-810s aboard the seaplane carrier Commandant Teste, and when the 7,580-ton cruisers of La Galissonniere type and the battleships Dunkerque and Strasbourg were commissioned from 1935 onwards they were equipped with floatplanes of the GL-810 series. On September 1, 1935, the fifth production GL-810 was sent to the Centre d'Etudes de Toulon for conversion as a target drone. After extensive trials with this aircraft, the workshops of the Saint-Mandrier Naval Air Station were instructed to convert a further five GL-810s as drones, and from September 1937, a number of machines were equipped as target tugs.
By the beginning of WW II, the GL-810 series floatplanes had been supplanted by later types aboard French warships, the old machines being handed over to shore-based units, and new units had been formed in August 1939 which included GL-810 series aircraft on their strengths. By September 20, 1939, Escadrilles 2S1 and 2S4 were operating GL-810s mixed with C.A.M.S. 55s and C.A.M.S. 37s respectively, 3S1 had eight GL-810 series floatplanes, 3S3 had six, 3S6 had three together with Levasseur P.L.15s, and 8S2 had four.
Initially, the GL-810s with the shore-based Escadrilles de Surveillance were used to patrol coastal waters, but they were progressively replaced by such types as the Loire 130. On May 10, 1940, Escadrille 1S2 had six GL-810 series floatplanes and three Late 29.0s, and Escadrille 3S3 possessed nine GL-810s. During the retreat from Lorient to Hourtin, 1S2's Gourdou-Leseurres were overloaded, carrying at least four men in addition to freight and equipment, but they were all captured by German forces at Hourtin late in June 1940. Escadrille 3S3 began conversion to the Loire 130 on June 18, 1940, and on July 14, 1943, Escadrille 17S still possessed two GL-810 series aircraft at Martinique.
Span: 52 ft 6 in (16.00 m)
Length: 34 ft 5 in (10.49 m)
Height: 13 ft 11.75 in (4.26 m)
Wing area: 462.848 sq.ft (43.00 sq.m)
Empty weight: 3,682 lb (1,670 kg)
Loaded weight: 5,423 lb (2,460 kg)
Max speed: 112 mph (180 kmh) at sea level
Cruise speed: 98 mph (158 kmh) at 3,281 ft (1,000 m)
Climb: to 9,843 ft (3,000 m) 16 min
Service ceiling: 18,045 ft (5,500 m)
Range: 348 mls (618 km) at 87 mph (140 kmh)."