Ten sample 10,000 yen notes and 68 blank notes were missing Thursday from the National Printing Bureau’s Ichigaya Center in Tokyo, police said.

The Ichigaya center, commonly known as the museum of bank notes and stamps, displays a stack of blank bank notes, topped by 10 10,000 yen sample notes, as part of an attraction designed to show visitors the weight of 100 million yen worth of 10,000 yen notes.

The display allows visitors to grab the stack through two holes on an acrylic case to feel the weight — about 10 kg.

The sample notes bear the fictitious serial number “A000000A” and the word “sample” is printed in red on the upper right corner of the bill. Otherwise, they have exactly the same design as the real thing, complete with watermarks.

Police said they fear the samples might be used in vending machines.

The stack of sample bills and blank notes were wrapped in a sheet of transparent polyethylene. Police said the sheet was cut open and later sealed with tape.

A security guard made the discovery that the sample and blank notes were missing at around 10:15 a.m., the police said.