Question: The TT pistol was developed as a replacement for the gas-seal revolver produced by whom?

Context paragraphs:
TT pistol: The TT-30 (Russian: "7,62-мм самозарядный пистолет Токарева образца 1930 года" , 7,62 mm Samozaryadnyj Pistolet Tokareva obraztsa 1930 goda, "7.62 mm Tokarev self-loading pistol model 1930", TT stands for Tula-Tokarev) is a Russian semi-automatic pistol.  It was developed in the early 1930s by Fedor Tokarev as a service pistol for the Soviet military to replace the Nagant M1895 revolver that had been in use since Tsarist times, though it ended up being used in conjunction with rather than replacing the M1895.  It served until 1952, when it was replaced by the Makarov pistol.

Nagant M1895: The Nagant M1895 Revolver was a seven-shot, gas-seal revolver designed and produced by Belgian industrialist Léon Nagant for the Russian Empire.

Colt Pocket Percussion Revolvers: The family of Colt Pocket Percussion Revolvers evolved from the earlier commercial revolvers marketed by the Patent Arms Manufacturing Company of Paterson, N.J.  The smaller versions of Colt's first revolvers are also called "Baby Patersons" by collectors and were produced first in .24 to .31 caliber, and later in .36 caliber, by means of rebating the frame and adding a "step" to the cylinder to increase diameter.  The .31 caliber carried over into Samuel Colt's second venture in the arms trade in the form of the "Baby Dragoon"-a small revolver developed in 1847–48.  The "Baby Dragoon" was in parallel development with Colt's other revolvers and, by 1850, it had evolved into the "Colt's Revolving Pocket Pistol" that collectors now name "The Pocket Model of 1849".  It is a smaller brother of the more famous "Colt's Revolving Belt Pistol of Naval Caliber" introduced the same year and commonly designated by collectors as the "1851 Navy Model" (and which was a basically a larger, .36 caliber of the Pocket Model, "belt pistol" referring to a weapon sized to fit into a belt holster, as opposed to the saddle holsters generally called for by Colt's larger cavalry combat models).  In 1855 Colt introduced another pocket percussion revolver, the Colt 1855 "Sidehammer", designed alongside engineer Elisha K. Root.

Marek Papała: Marek Papała (September 4, 1959 – June 25, 1998) was a Polish police officer, and Chief of Police from January 3, 1997 – January 29, 1998, who died as a result of a gunshot head wound from a silenced TT pistol on June 25, 1998.  Officially Papała died at the hands of a car thief turned state witness Igor L. Due to numerous inaccuracies the investigation was criticized by many former police officers and journalists

ISSF 50 meter pistol: The 50 meter pistol, formerly and unofficially still often called free pistol, is one of the ISSF shooting events.  It provides the purest precision shooting among the pistol events, and is one of the oldest shooting types, dating back to the 19th century and only having seen marginal rule changes since the 1936.  Most of the changes concern distance (30m, 50m, 50 Yards), caliber (.22 .22lr .44CF), type of pistol (revolver only, revolver or pistol, any pistol), and time allowed (16 hours, 6 hours, 3 hours, 2 hours, 1 hour and 15 minutes) and, most recently, format of the finals (carry over scores, start from zero, amount of shots fired in the finals).  The target of this event has never changed since 1900, and the distance since 1912.  Competitors have been using the single shot 22 rim-fire pistol since 1908.  The sport traced back to the beginning of indoor flobert Pistol parlor shooting in Europe during the 1870s, which in turn traced back to 18th century pistol dueling.

Korth Combat: Korth Combat is a German high-end revolver produced by Korth GmbH chambered in .357 Magnum.  Each revolver is custom made and costs over $US5000.

Combat (photograph): Combat is a black-and-white photograph by the Soviet photographer Max Alpert.  It depicts a Soviet military officer armed with a TT pistol who is raising his unit for an attack during World War II.  This work is regarded as one of the most iconic Soviet World War II photographs, yet neither the date nor the subject is known with certainty.  According to the most widely accepted version, the photograph depicts Aleksei Gordeyevich Yeryomenko, minutes before his death on 12 July 1942.

Modèle 1892 revolver: The Model 1892 revolver (also known as the "Lebel revolver" and the "St. Etienne 8mm") is a French service revolver produced by Manufacture d'armes de Saint-Étienne as a replacement for the MAS 1873 revolver.  It was the standard issue sidearm for officers in the French military during the First World War.

Smith &amp; Wesson Model 60: The Smith & Wesson Model 60 revolver is a 5-shot revolver that is chambered in either .38 Special or .357 Magnum calibers.  It was the first revolver produced from stainless steel.

Pfeifer Zeliska .600 Nitro Express revolver: The .600 Nitro Express Zeliska revolver is an Austrian single-action revolver produced by Pfeifer firearms.  Except for the Giant 1859 28mm Remington revolver, the Zeliska may be the largest handgun in the world, weighing in at 6.001 kg and having a length of 55 cm .  The cylinder section alone weighs 2.041 kg .  The Zeliska is one of the most powerful handguns in the world, producing a muzzle energy of 7,591 foot pounds.  The weight of the handgun helps control the recoil, making controlled shooting possible.  The capacity of a Zeliska is five .600 Nitro Express or .458 Win Mag rounds.  The Zeliska fires a .600 Nitro Express slug (900 grain) at 1,950 ft/s (594.36 m/s, 2,139.7 km/h).  The cost of a Zeliska revolver is $17,316.  Each .600 Nitro Express round costs $40, making this gun very expensive to fire.

Supporting paragraphs: TT pistol Nagant M1895
Answer: Léon Nagant