Question: What gun used in World War I, World War II, Korean War and Vietnam War is Sig Sauer GSR ("Granite Series Rail") modeled after?

Context paragraphs:
M1911 pistol: The M1911 is a single-action, semi-automatic, magazine-fed, recoil-operated pistol chambered for the .45 ACP cartridge.  It served as the standard-issue sidearm for the United States Armed Forces from 1911 to 1986.  It was widely used in World War I, World War II, the Korean War, and the Vietnam War.  The pistol's formal designation as of 1940 was Automatic Pistol, Caliber .45, M1911 for the original model of 1911 or Automatic Pistol, Caliber .45, M1911A1 for the M1911A1, adopted in 1924.  The designation changed to Pistol, Caliber .45, Automatic, M1911A1 in the Vietnam War era.

USS Piedmont (AD-17): USS "Piedmont" (AD–17) was a "Dixie"-class destroyer tender built during World War II for the United States Navy.  Her task was to service destroyers in, or near, battle areas and to keep them fit for duty.  She served in the Pacific Ocean during World War II, the Cold War, the Korean War, and the Vietnam War.  For her work in battle areas she won four battle stars for her Korean War efforts and one for Vietnam War service.

USS Valley Forge (CV-45): USS "Valley Forge" (CV/CVA/CVS-45, LPH-8) was one of 24 "Essex"-class aircraft carrier s built during and shortly after World War II for the United States Navy.  The ship was the first US Navy ship to bear the name, and was named after Valley Forge, the 1777–1778 winter encampment of General George Washington's Continental Army.  "Valley Forge" was commissioned in November 1946, too late to serve in World War II, but saw extensive service in the Korean War and the Vietnam War.  She was reclassified in the early 1950s as an attack carrier (CVA), then to an antisubmarine carrier (CVS), and finally to an amphibious assault ship (LPH), carrying helicopters and marines.  As a CVS she served in the Atlantic and Caribbean.  She was the prime recovery vessel for an early unmanned Mercury space mission.  After conversion to an LPH she served extensively in the Vietnam War.  "Valley Forge" was awarded eight battle stars for Korean War service and nine for Vietnam War service, as well as three Navy Unit Commendations.

SS Red Oak Victory: SS "Red Oak Victory" is a U.S. military Victory ship of the "Boulder Victory"-class cargo ship used in the Second World War.  She was preserved to serve as a museum ship in Richmond, California, and is part of the Rosie the Riveter/World War II Home Front National Historical Park.  She was one of 534 Victories built during World War II, but one of only a few of these ships to be transferred from the Merchant Marine to the United States Navy.  She was named after Red Oak, Iowa, which suffered a disproportionate number of casualties in early World War II battles.  (Montgomery County ranked third among Iowa counties in World War II casualties per capita).  The ship was active during World War II, the Korean War, and the Vietnam War.

Sac City Monument Square Historic District: Sac City Monument Square Historic District is a nationally recognized historic district located in Sac City, Iowa, United States.  It was listed on the National Register of Historic Places in 2015.  The square consists of the General Sherman Hall (1892), Memorial Statue (1894), the American Legion Hall (1922), four World War II era Howitzers, and three granite tablets that commemorate the lives of the soldiers from Sac County who fought in World War I, World War II, the Korean War, and the Vietnam War.  The Vietnam War tablet does not contribute to the historic district because it is a more recent installation.

USS Caliente (AO-53): The USS "Caliente" (AO-53) was a "Cimarron"-class fleet oiler built during World War II for the U.S. Navy.  During her career in the Pacific Ocean, "Caliente" participated in World War II, the Korean War, and the Vietnam War.  She was highly decorated for fulfilling her dangerous mission of carrying fuel into battle areas.  She received 10 battle stars for World War II, 4 for the Korean War and 8 campaign stars for the Vietnam War.

SIG Sauer 1911: The SIG Sauer GSR ("Granite Series Rail") is a series of pistols with a stainless steel frame and slide based on the M1911 by SIG Sauer.  The SIG Granite Series was awarded the 2004 Handgun of the Year Award by the Shooting Industry Academy of Excellence.  It is entirely made in the USA, from American parts.

George Juskalian: George Juskalian (Armenian: Գևորգ Ժուսգալեան ; June 7, 1914 – July 4, 2010) was a decorated member of the United States Army who served for over three decades and fought in World War II, the Korean War and the Vietnam War.  Following graduation from Boston University, Juskalian entered the army as a second lieutenant in June 1936.  During World War II, he served with the infantry during the North African Campaign and took part in Operation Torch.  At the Battle of the Kasserine Pass, he was captured by German troops and became a prisoner of war (POW) for twenty-seven months.  During the Korean War he commanded an infantry battalion.  He was then stationed in Tehran where he acted an advisor to the Imperial Iranian Army throughout 1957 and 1958.  During the Vietnam War, Juskalian once again undertook advisory duties, working with the South Vietnamese Army between 1963 and 1964, before serving as the MACV inspector general under General William Westmoreland.

T1 tanker: The T1 tanker or T1 are a class of sea worthy small tanker ships used to transport fuel oil before and during World War II, Korean War and Vietnam War.  The T1 tanker classification is still in use today.  T1 tankers are about 200 to 250 feet in length and are able to sustain a top speed of about 12 knots.  The hull designation "AO" is used by the US Navy to denote the ship is a T1 oil tanker and "AOG" that the T1 is a gasoline tanker.  The small size allows the T1 to enter just about any sea port or to anchor around a small island, this was very useful during the Pacific War.  The T1 tanker can carry about 48,000 to 280,000 BBLs.  Some T1 tankers were used to transport goods other than oil, a few were used for black oil-crude oil, diesel, chemicals and rarely bulk cargo like grain.  T1 tankers are also called liquid cargo carriers.  The T1 tanker has about a 6,000 to 35,000 DWT of cargo.  The small size also gives the ships short turn around time for repair, cleaning, loading and unloading.  A T1 tanker carrying dirty cargo, like crude oil needs a few weeks of labor to clean before carrying clean cargo.  Most T1 ships during World War II were named after major oil fields. T1 tanker are operated by the US Navy, War Shipping Administration and United States Maritime Commission.  Some T1 were loaned to England in the Lend-Lease program for World War II, after the war most were returned to the USA.  After World War II many of the T1 ships were sold to for civilian use.  Each T1 had emergency life rafts on the boat deck.  The ships had cargo booms and piping to load and unload fuel.  During war time the T1 are armed for protection with deck guns.  A typical ship may have one single 3"/50 dual purpose gun, two 40 mm guns and three single Oerlikon 20 mm cannon.  A T1 at war time normally had a crew of 38 and up to 130.  If operating as a United States Merchant Marine ship, the crew would be a mix of civilian Merchant Marines and United States Navy Armed Guards to man the guns.

PM M1910: The PM M1910 (Russian: Пулемёт Максима образца 1910 года, "Pulemyot Maxima obraztsa 1910 goda" or "Maxim's machine gun model 1910") was a heavy machine gun used by the Imperial Russian Army during World War I and the Red Army during Russian Civil War and World War II.  Later, the gun saw service in the Korean War and the Vietnam War, and some have been spotted in the War in Donbass.

Supporting paragraphs: SIG Sauer 1911 M1911 pistol
Answer: M1911