cR0w 
🏴☠️I made a design for a pink pony patch for someone but he changed his mind so I figured I'd share it here in case anyone else wanted to make patches or stickers with it. Nothing fancy but I thought it was fun.
Juho MäntysaloThank-you for the idea.
XenoPhage 
@XenoPhage @iju No problem. I figured it could explain it better than I.
@XenoPhage @iju It's a lot better than the "ZOMG Antifa Extremists!" that I see all over the place. :-/
I did have a short explanation in the alt-text, which I'll repeat here with some clarification: they are the three arrows (as in: from a [cross]bow) to strike at the heart of ideologies against peoples' self-determination: capitalism, monarchism, and vanguardism [eg. Soviet communism].
It's a symbol that's used by antifascists, socialists, anarchists, and left-leaning social democracts.
EDIT: It's a very good thing you asked. Asking questions makes us all smarter :)
@iju @XenoPhage I used to read all the alt text until Mastodon changed and it no longer pops up when I hover over the image. I miss that feature. Finding the little ALT tag to click throws me off.
I'm sure there are alternative user-interfaces more suitable for your favourite form of GUI navigation, but alas I wouldn't be the right person to ask for help.
But I'll repeat that I'm very happy I was asked for clarification. There's certainly more than one person who for one reason or another left my alt-text unread.
Dave Wilburn 
To clarify, and someone more knowledgeable please correct me where I'm wrong, I believe the "three arrows" symbol of the SPD-aligned Iron Front represented opposition to monarchism, fascism, and communism.
@DaveMWilburn @iju @XenoPhage That's how I remember it. Anti fascism, anti communism, and anti reactionary conservatism / monarchism.
@DaveMWilburn @XenoPhage @cR0w
Communism in the context of the Iron Front referred to Soviet Union [note the symbol to which the arrow is directed].
Soviet Union's ideology was vanguardism. It was a core-leninist idea about a small ruling group ("professional revolutionaries") being the best choice to advance communism.
EDIT: You can spot the similarities to fascism and monarchism.
EDIT2: Heavy edits to add clarity. (Hopefully.)
@DaveMWilburn @XenoPhage @cR0w
You are allowed to disagree. Personally I feel this distinction is one of those hills worth dying for, as the alternative makes the symbol over-defined, and subject to be used in a nihilistic fashion, and/or to support the horseshoe theory.
(Everything is bad, and as such present which doesn't require system-changes is the best choice.)