This is the head of Portugal's first serial killer, Diogo Alves, who murdered 70 people in the 19th century. His head was cut off, then preserved in a jar in 1841. 182 years later, his head remains in that same jar on display at The University of Lisbon.
I had a phase during the first pandemic lockdown where I'd race to the fridge to get the mostly-empty honey mustard bottle and make fart noises to blow the remaining contents onto plain Greek yogurt