Read in Catalan

A demonstrator at the Spanish unionist march called by the country's police union Jusapol on Saturday morning in Barcelona bore a Nazi tattoo. As Catalunya Radio journalist Albert Mercadé revealed in a tweet, the man had a Totenkopf tattooed on his neck. 

Translation: One of the participants today in the JUSAPOL demonstration. On his neck he has a Totenkopf, symbol of the 3rd division of the Waffen SS, paramilitary force in Nazi Germany— Albert Mercadé

The Totenkopf (which translates literally as corpse's head, ie, skull) is an insignia that was used by different German military and paramilitary bodies during the Nazi era. In particular, as Mercadé points out, the symbol that the man has tattooed under his left ear was the ensign of the third division of the Waffen-SS combat unit.