The knife's double-edged blade is 6.75 in (17.1 cm) long. The handle is cast in bronze. It ends in a steel nut that holds the blade in place, and expands laterally in four bows for each knuckle. These in turn have spikes to prevent an opponent from grabbing the knife hand. Besides the blade, both the nut ('skull-crusher') and the bows (as brass knuckles) can also be used offensively, making the Mark I three weapons in one.
Season 1 EditJimmy plays five finger filet with his trench knife at the Four Deuces while Kitty and other prostitutes watch. Al Capone approaches and asks if Jimmy is crazy. Jimmy wonders if Capone played the game during the war and Capone claims that he did but refuses to participate, saying that Johnny Torrio is on his way. Jimmy returns the knife to its sheath in his boot and covers it with his trouser leg. When Torrio enters he says that he has arranged a sit-down with Irish American gangster Charlie Sheridan to arrange for Torrio's withdraw from Greektown. Jimmy convinces Torrio to keep the meeting, but as part of a plan to take out Sheridan.
At the meeting, Sheridan has Torrio, Capone and Jimmy searched to make sure that they are not armed. After they sit down and negotiate, Jimmy shifts in his chair, crosses his legs and exposes his trench knife in its holster. One of Sheridan’s men notices and shouts, they all draw their weapons. Sheridan’s second retrieves the knife and Sheridan chastises his other men for their inattention in the search. Jimmy apologises and claims he forgot that the knife was there. Sheridan holds the knife to Jimmy’s throat and threatens to give him a reminder. Sheridan notices a metal stud on the base of the handle. Jimmy elucidates that it is called a skull crusher and can be used to crack walnuts. Sheridan says that he will try it out and pockets the knife. He puts his guns away and returns to discussing business.
The meeting over, Torrio says he needs to use the bathroom. Capone says that they will bring the car around. Sheridan tips the coat checker and notes that she has been replaced. The new girl says that the blonde is on a coffee break and then hands Capone and Jimmy their coats, revealing her face; it is Kitty from the Four Deuces. She nods to Jimmy and he thanks her. She ducks behind the counter as he turns and shoots two of Sheridan’s men. Sheridan’s second moves to draw a pistol and Capone pulls a shotgun from under his coat and kills him. Jimmy shoots Sheridan and the abdomen and Torrio leaves, telling them to wrap it up. Jimmy tells the other’s to go and grabs Sheridan and puts his pistol under his chin. He tells Sheridan that Greektown belongs to them now and then fires. He retrieves his knife from the corpse and then gets into the car. ("Family Limitation")
Jimmy later uses his trench knife to slash Leo D'Alessio's throat while he is in the barber, following orders of Nucky Thompson. While Leo bleeds out helplessly, Jimmy calmly cleans his knife on Leo's sheath and puts the knife back on his boot before leaving. ("A Return to Normalcy")
Season 2 EditJimmy unsheathes his knife outside Meyer Lansky's game and puts it on the back of his trousers before setting a trap for Incrocci and Scarpelli, two of Joe Masseria's thugs. The two appear while Jimmy waits for them in front of the fountain of Temperance in Tompkins Square Park and attempt to rob him of what he won at Lansky's game - as Jimmy had predicted. One of the thugs searches Jimmy while the other has him at gunpoint; he takes Jimmy's gun but misses his knife. Jimmy tells them that he put the money in his boot. When the thug bends to take the money, Jimmy quickly takes the knife, hits the nearest thug with the skull-crusher and slashes the throat of the other. Jimmy then grabs the first thug, throws him against the fountain and stabs him in the back. He then leaves the two to bleed to death. ("Ourselves Alone")
Jimmy has his knife on when he returns to Atlantic City from Princeton and while he listens as his mother plans how to handle Angela’s murder. She talks of arranging a funeral for appearance's sake. She notes that there will be few mourners given Angela’s narrow circle. She tells Jimmy that Angela's girlfriend Louise, found dead next to her body, was from out of town and that the police are trying to reach her relatives but that it is not their concern. She says that they need to consider Tommy and reveals that she has told him that his mother went away to paint for a few days. She suggests telling Tommy that Angela went to live with her friends in Paris and wanted him to stay with them. She brazenly claims that Tommy will forget Angela in a month. Hearing this, Jimmy rushes across the room and chokes Gillian, repeating over and over that he will remember. His father, Louis Kaestner, stabs him in the shoulder with an antique spear. Jimmy falls to the floor and Gillian sucks in air. The Commodore pulls back the spear and Jimmy flips over and grabs it as his father tries to drive it into his chest. They grapple with the weapon and Jimmy gets to his feet before being pushed back against the wall. The Commodore attempts to choke Jimmy with the weapon as Gillian screams no from her seat. Jimmy then stabs his father in the abdomen with his trench knife. The Commodore drops the spear and stumbles backwards, the blade still in place. Gillian shouts at Jimmy to finish it after he rips the weapon free. Jimmy stabs his father in the chest and he collapses to the floor, twitching. Jimmy limps into the next room and then drops to the ground, unconscious. ("Under God's Power She Flourishes")
Jimmy leaves his trench knife at The Commodore's home after Nucky phones him and tells him to meet in the Atlantic County Great War Memorial, saying that he is going to hand Manny Horvitz to exact revenge for the death of Angela. He knows that it is a trap and that Nucky is going to kill him, and he accepts it. At the meeting place, Jimmy announces that he is not armed as Owen Sleater searches him. Eli Thompson reminds Owen to look in his boot for the knife. Owen still finds nothing and confirms that Jimmy is indeed unarmed. ("To the Lost")
|Season one appearances|
|Boardwalk Empire||The Ivory Tower||Broadway Limited||Anastasia|
|Nights in Ballygran||Family Limitation||Home||Hold Me in Paradise|
|Belle Femme||The Emerald City||Paris Green||A Return to Normalcy|
|Season two appearances|
|21||Ourselves Alone||A Dangerous Maid||What Does the Bee Do?|
|Gimcrack & Bunkum||The Age of Reason||Peg of Old||Two Boats and a Lifeguard|
|Battle of the Century||Georgia Peaches||Under God's Power She Flourishes||To the Lost|