I guess getting your message across to fellow members, before the advent of mass media, was by portrait.
Here below, for example, men who have been involved in shaping past historical events portrayed with hand in jacket.
The traditional explanation is....
The pose traces back to classical times Aeschines, founder of a rhetoric school, suggested that speaking with an arm outside one's toga was bad manners. Arline Meyer, in her essay "Re-Dressing Classical Statuary: The Eighteenth-Century 'Hand-in-Waistcoat' Portrait," notes the pose being used in eighteenth century British portraiture as a sign of the sitter's breeding. Francois Nivelon's A Book Of Genteel Behavior of 1738 noted the hand-inside-vest pose denoted "manly boldness tempered with modesty." - Wiki
However, another interpretation put forward is that...
Uncovering the Hidden Hand https://www.bibliotecapleyades.net/sociopolitica/codex_magica/codex_magica04.htm#FOURIn the early degrees, the Mason is told that the name of God has been lost. He's even told that he should use a substitute name for God, MAHABONE. But later, after he's swallowed whole the rotten fabric of degree ritual after degree ritual, the bamboozled and propagandized fellow is finally told that the one he is to worship goes by the name Jahbuhlun and that he is now ready to declare himself, a man, as the great I AM.
Obviously, the Illuminati's Masonic elite do not want the general public to know these terrible things. After all, incredibly, Freemasonry's public image is that it is some kind of "Christian" group. So, the pretense must be maintained and the secrets buttoned up from the "profane and vulgar" masses (you and me, dear reader).
Therefore, the name of the horrible God whom the Masons worship must stay hidden.
The name and identity of the hidden God must be concealed at all costs, and thus an appropriate hand sign has been devised to represent this grotesque coverup: the Sign of the Hidden Hand. 
1700's
Wolfgang Amadeus Mozart (1756-1791). Freemason and Austrian composer. Died at age 35. Initiated in Austrian lodge Zur Wohltatigkeit on Dec. 14th 1784. Painting c. 1777. Note: Mozart's father Leopold Mozart, was also a Freemason and composer.

Marquis de Lafayette (1757-1834). 33° Freemason and French military officer who was a general in the American Revolutionary War and a leader of the Garde Nationale during the bloody French Revolution. Lafayette was also made an honorary Grand Commander of Supreme Council of New York. More than 75 Masonic bodies in the U.S. have been named after him, including 39 lodges, 18 chapters, 4 councils, 4 commanderies, and 7 Scottish rite bodies.

Salomon Rothschild (1774-1855) - Vatican treasury banker. Wealthy Jewish(?) founder and overseer of the Vienna, Austria branch of the Rothschild clan.

Simón Bolívar (1783-1830) Freemason. Known as the "George Washington of South America" Bolívar used genocidal terror tactics to achieve his aims. He joined Freemasonry in Cadiz, Spain and received the Scottish Rite degrees in Paris and was knighted in a Commandery of Knights Templar in France in 1807. Bolívar founded and served as master of Protectora de las Vertudes Lodge No. 1 in Venezuela. The country of Bolivia is named after him. Bolívar also served as the president of Columbia, Peru, and Bolivia in the 1820's. Belonged to the Order and Liberty Lodge No. 2, Peru.

Napoleon I (1769-1821) . Freemason and Emperor of France, 1805-14. Napoleon's four brothers - Joseph, Lucian, Louis, and Jerome, as well as his stepson, Eugene Beauharnais, his brother-in-law Murat, and nephew, Jerome, were all Freemason's. Most of them held high Masonic rank. Those who were chosen by Napoleon for high honor and office in the state were usually Freemason's. Of the six, who, with the emperor himself, formed the Grand Council of the Empire, five were certainly Freemasons, including Arch Chancellor Prince Jean Jacques Regis Cambaceres, an enthusiastic and active Mason. Of the nine lesser imperial officers of state, six at least were active Masons. Of the marshals of France who served under Napoleon, at least 22 of the first 30 were Freemasons.

Seth Read (1746-1797). The man Instrumental in putting the Latin motto and popular Masonic phrase: "E PLURIBUS UNUM" (Out of Many, One) on U.S. coins

Thomas Cochrane (1775-1860) Royal Navy officer and radical politician

Abraham Whipple (b. 1733 - d. 1819). American revolutionary naval commander



George Washington (b. 1732 - d. 1799)

Francisco Pizarro (1471-1541). Spanish conquistador and murderer of indigenous peoples in South America.
1800's

William Ewart Gladstone (b. 1809 - d. 1898) British Liberal Party statesman and four times Prime Minister of the United Kingdom (1868–74, 1880–85, 1886 and 1892–94)

William Tecumseh Sherman (b. 1820 - d.1891) Ruthless American Civil War Union general. His total war polices of "scorched earth" against the South, have earned him the reputation as the first 'modern general'

Karl Marx (b. 1818 – d. 1883) German - Jewish revolutionary and communist icon.

Trotsky


Vladimir Lenin, who led the Communist overthrow of the Czar in Russia.

Mikhail Levandovsky (center). These three men were deeply involved in the bloody 1917 Communist Russian Revolution
https://worldtruth.tv/in-the-shadow-of-hermes/