This is a very interesting flag!
The Sieg rune is also known as the Sigel rune - in Anglo Saxon 'Sowilo' and Armanen 'Sig', and means 'Victory' as a National Socialist rune. The Single Sieg rune was the emblem for the Deutsches Jungvolk. The Schutz-Staffel used the double Sieg rune as their emblem, with only racial-Germanic soldiers being allowed to wear the runes on their collars.
The Svensk Socialistisk Samling (SSS) (who had been previously called National Socialist Worker's Party / NSAP) even used the triple Sieg rune pattern - SSS!
The flag above with the gothic style 'York' under a single Sieg rune caught me in my tracks when I first saw it - thinking the name 'York' was referring to city of York in the North of England. However the flag isn't English, but was a banner from the American German Bund (Amerikadeutscher Volksbund).
Triple Sieg pattern of the Swedish National Socialist workers Party.