Hank describes Congresswoman Welch as being "ISTP on the old Myers-Briggs, which is still the gold standard for personnel." Hank is referring to the Myers-Briggs Type Indicator (MBTI) system, a personality test developed during World War II by Americans Katharine Cook Briggs and her daughter Isabel Briggs Myers, based on psychiatrist Carl Gustav Jung's 1921 book "Psychological Types", with the goal of helping women entering the industrial workforce for the first time identify war-time jobs to which they may be well-suited. The system categorizes individuals into 16 distinct "personality types" by assigning a letter to a set of four categories: Extraversion or Introversion, Intuition or Sensing, Feeling or Thinking, and Judgment or Perception. The letters are assigned based on a series of questions the subject answers, producing a four-letter test result, such as "ISTP" in the case of Congresswoman Welch. ISTP indicates she exhibits Introversion, Sensing, Thinking, and Perception. According to the MBTI, an ISTP is a "craftsperson" and "virtuoso"; they are people who are logical, hands-on, action-oriented, prefer spontaneity, enjoy troubleshooting, and value their independence. Despite the MBTI still being a fairly popular personality test for the general population, often used by personal development coaches and websites, professional psychologists and psychiatrists consider it to be little more than pseudoscience and don't consider it a valid or reliable personality test for clinical purposes. The questions developed for the MBTI are vague and general enough to apply to a broad range of people (known as the Barnum effect [after P.T. Barnum]), relying on flattery and confirmation bias to lead participants to identify with descriptions that are vague and considered desirable and applicable by society.
The tiny revolver The Ghoul gives to Lucy, which he previously used in The Innovator (2025), is a real pistol known as a Knuckle Duster revolver, and was marketed by the name "My Friend". The original knuckle duster was a very small pocket revolver manufactured by Irish-born gunsmith James Reid around 1868, it was available in .22 Short, .32 Rimfire, and .41 Rimfire caliber models, although the .22 was the most common. In order to be ultra-concealable the knuckle duster has no barrel, allowing it to easily fit in a man's vest or trouser pocket, as such it was designed to be used during hand-to-hand combat and fired at extreme close-range, with the pistols' effective range being only 1-3 yards (0.91-2.74 meters); knuckle dusters were also commonly carried by women for self defense, as they easily fit inside a purse, or could be tucked into a garter belt or bra. The knuckle duster's name comes from its brass grip, which has a thumb hole with a large bow (knob) at the end of the grip that could be utilized to bludgeon an adversary. Reid created this dual-purpose self-defense tool with a strategy in mind, believing that not every altercation should end in a fatality, when asked about this gun's unique design Reid said "Never shoot a man if you can knock him down."
The Knuckle Duster is similar to another pocket revolver known as an Apache revolver, which incorporated additional melee weapons designed to compliment the gun's extreme close-range use. The Apache revolver is attributed to French gunsmith Louis Dolne and was originally made in the late 1860's to early 1870's, it was originally chambered in 7mm (.27 caliber) Lefaucheux, a French pinfire cartridge; pinfire was an early type of metallic cartridge predating rimfire and centerfire, which had a small pin protruding from the side of the cartridge that acted as a firing pin when struck by the gun's hammer. The Apache used a fold-over style of brass knuckle, also called knuckle dusters, as a grip, and included a rudimentary foldout dual-edged knife attached to the front of the gun. The Apache revolver became notorious for its use by French underworld figures of the early 1900's known as Les Apaches, leading to its name. A version of the Apache revolver was made in England in the 1930's chambered in 9×19mm Parabellum, and was allegedly used by British Commandos during World War II. Modern replicas of both the Knuckle Duster and Apache revolver have been made, and are usually chambered in either .22 LR, .22 Magnum, .32 ACP, or .38 Special.
The Knuckle Duster is similar to another pocket revolver known as an Apache revolver, which incorporated additional melee weapons designed to compliment the gun's extreme close-range use. The Apache revolver is attributed to French gunsmith Louis Dolne and was originally made in the late 1860's to early 1870's, it was originally chambered in 7mm (.27 caliber) Lefaucheux, a French pinfire cartridge; pinfire was an early type of metallic cartridge predating rimfire and centerfire, which had a small pin protruding from the side of the cartridge that acted as a firing pin when struck by the gun's hammer. The Apache used a fold-over style of brass knuckle, also called knuckle dusters, as a grip, and included a rudimentary foldout dual-edged knife attached to the front of the gun. The Apache revolver became notorious for its use by French underworld figures of the early 1900's known as Les Apaches, leading to its name. A version of the Apache revolver was made in England in the 1930's chambered in 9×19mm Parabellum, and was allegedly used by British Commandos during World War II. Modern replicas of both the Knuckle Duster and Apache revolver have been made, and are usually chambered in either .22 LR, .22 Magnum, .32 ACP, or .38 Special.
The song playing during the final scene is "This Is Worth Fighting For", performed by The Ink Spots in 1942. Ink Spots' songs have been featured across the Fallout series: Their 1940 performance of "Maybe" plays during the intro cinematic and credits of Fallout (1997), in Fallout 2: A Post-Nuclear Role-Playing Game (1998) a man named Martin in Vault 8 sings part of the song, it plays on Galaxy News Radio in Fallout 3 (2008), Diamond City Radio in Fallout 4 (2015), and Appalachia Radio in Fallout 76 (2018). Their 1944 performance of "Into Each Life Some Rain Must Fall" plays on Galaxy News Radio in Fallout 3 (2008), and on Diamond City Radio in Fallout 4 (2015). Their 1979 performance of "It's a Sin to Tell a Lie" is broadcast on Radio New Vegas, Mojave Music Radio, and Black Mountain Radio in Fallout: New Vegas (2010). Their 1947 performance of "It's All Over But the Crying" appeared in the first trailer for Fallout 4 (2015) and is broadcast on Appalachia Radio in Fallout 76 (2018). Their 1941 performance of "I Don't Want to Set the World on Fire" appears in Fallout 3 (2008), Fallout 4 (2015), and Fallout 76 (2018). And their 1940 performance of "We Three (My Echo, My Shadow and Me)" is broadcast on Appalachia Radio in Fallout 76 (2018).
(At 20:10) The song playing during the flashback in the airport is "I've Got You Under My Skin", performed by Frank Sinatra in 1956. Sinatra's 1961 cover of "Blue Moon" is used in the teaser trailer for Fallout: New Vegas (2010) and is broadcast on Radio New Vegas in the game, it was also used in a promotional trailer for the DLC expansion Fallout 76: Once in a Blue Moon (2023). Additionally, the names of several quests in Fallout: New Vegas (2010) are references to some of Sinatra's signature songs including: "One for My Baby", "Come Fly With Me", "My Kind of Town", and "Ring-a-Ding-Ding!".
