I have a theory for you to shoot down.
I believe this is an ‘Ulster Loyalist’ pin. Perhaps not from any kind of official organisation, but worn as an expression of political and religious support for the Irish province of Ulster remaining part of the United Kingdom. A little history first:
The hand is, I think, symbolic for Ulster and has been used as their emblem for centuries. It’s usually shown as a right hand, and in red if coloured, but you’ll commonly see it in silver or gold on unenamelled jewellery… especially rings. Also known as the “Red Hand of Ulster”, like this one, which also carries a political message:
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In 1688, we had our ‘Glorious Revolution’… a largely bloodless overthrow of the Catholic monarchy by a popular uprising following an invasion by the staunchly Protestant William of Orange from the Dutch Republic. William’s army was pretty much invited to come an invade us to stem the rise of Catholicism and he took the throne as William III of England (William II of Scotland). William was popularly known as ‘King Billy’ and became the poster child for Protestantism thereafter, with Ulster Loyalists becoming known as ‘Billy Boys’. All of this suited the province of Ulster in the North of Ireland, which was largely protestant, but not the southern parts of Ireland which were predominantly Catholic. Hence the deep divisions in Irish politics that ultimately led to partition in 1921, with six of Ulster’s nine counties becoming the state of ‘Northern Ireland’ and remaining loyal to the monarchy.
The Ulster Loyalist movement emerged in the late 19th Century in direct response to the Irish Home Rule movement, and the rise of Catholic Irish nationalism. Ulster was popularly referred (at least by its own residents) as “The Cock o’ the North” and that imagery was used in political propaganda, and also referenced in one of their ‘battle-cry’ songs: “Fight for Billy, Fight for Billy, Fight for the Cock o’ the North…” Here’s a piece of Loyalist propaganda in the form of a postcard, reinforcing their opposition to Home-Rule for Ireland:
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I think someone has put the two elements together in that pin as an expression of Ulster’s loyalty, which would probably put it somewhere in the late 1800s or early 1900s.