Nazi officials are seen partying with a pipe-smoking dog in newly unearthed footage.
It shows SS members, German soldiers, and even a high-ranking naval officer alongside hotel staff.
According to researchers, films like this are exceptionally rare.
A rusty old tin containing the reel was donated anonymously to local authorities.
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And Harco Gijsbers, of the NIOD Institute for War, Holocaust and Genocide Studies, said he had never seen anything like it in all his years of work.
The clip, which has no audio, shows the officials laughing, drinking, smoking, and dancing – and even enjoying the antics of a German Shepherd wearing a party hat, glasses, and a pipe.
It was filmed during the German occupation of the Netherlands at the former Hotel Proot in Alkmaar, north of Amsterdam, as reported by Need To Know.
Gijsbers said the interactions were unusual because the groups shown didn’t always get along.
Authorities are still trying to identify the Nazi officials.
Hotel owner and staff are also seen apparently enjoying the festivities.
The hotel stood in the middle of the high street where a clothing store now stands.
Jesse van Dijl of the Regional Archives said collaboration with the Germans wasn’t uncommon at the time.
He said: “For many people, it was a way to get through the difficult times.
“These kinds of videos, showing Dutch people partying with the Germans, were, of course, massively burned after the liberation.
“The footage could be used as evidence against the Dutch people depicted in them.
“Photos of these kinds of situations aren’t unique, but moving images are.”
Van Dijl explained the film was part of a larger legacy left to the woman who donated it, adding: “She didn’t have the opportunity to view the footage so she had no idea what was on it.”
The hotel frequently hosted Nazi meetings, and Anton Mussert, leader of the NSB (National Socialist Movement), dined there.
Movie nights were also held at the venue.
Gijsbers said: “The owner was quite pro-German.”
Relatives of the former hotel owner have also seen the footage.
Van Dijl said: “They found it painful and moving.
“They’ve come to know their grandfather, who received a heavy sentence after the war, as a kind man.
“But they also recognise that the historical footage is special.”
The eight-minute video begins with a parade before cutting to the lively hotel scenes.
Van Dijl believes it was filmed during the winter of 1941-1942.
The dog is thought to have been a mascot for the military unit.
Lip readers examined the footage but “unfortunately they couldn’t make head nor tail of it”, van Dijl said.
He added: “We hope to find someone who can help us.”
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