FILE No.23Unsolved
A vase stolen from the secondhand shop Kura Antiques turned up on the black market. An old appraisal certificate came with it. But there were four certificates, all dated February 29.
On all four, the seals and handwriting look genuine, and you cannot tell them apart by appearance. Even so, exactly one is forged.
Which certificate is the forgery? Look closely at the scene plan and the evidence.
If you get stuck, open the hints one at a time, in order.
What kind of year has a February 29?
Is every year divisible by 4 one of them? Watch out for multiples of 100.
Check whether 1900 is divisible by 100, and whether it is divisible by 400.
Which certificate is the forgery? Look closely at the scene plan and the evidence.
Choose the answer closest to the truth.
3. Certificate dated 1900 (Kashiwagi)
The answer is “3. the certificate dated 1900 (Kashiwagi).”
February 29 exists only in leap years. A leap year is a year divisible by 4. But a year divisible by 100 is not a leap year, except that a year divisible by 400 is.
1892, 1896 and 1904 are divisible by 4 but not by 100, so they are leap years. February 29 really existed in them, so certificates 1, 2 and 4 are not contradicted.
1900, however, is divisible by 4, but also by 100, and not by 400. It falls under the exception, so it was not a leap year, and February had only 28 days. There was no such day as February 29, 1900, so certificate 3 is the forgery.
The seals and handwriting looked genuine on all four. Appearance gave no basis for deciding. Checking whether the date itself exists was the key to spotting the forgery.
Because 1900 is divisible by 4, it is easy to assume it was a leap year.
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