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Can dial locks, such as the one below, have repeated numbers in their combination? For example, the combination 10-39-10 has the number 10 repeated twice in it. If so how often is this the case?

A dial lock

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  • for the first and third number, yes. for the middle number no, it needs a physical separation\ distance of about 1/8th a turn. – dandavis Nov 8 '17 at 21:30
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Yes, these locks can have repeated first and third digits, which occur about one in 10 times. See Samy Kamkar's page on Master locks to learn more about them.

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  • I don't see where it says these locks can have repeated first and third digits in the source you provided. – Unknown Nov 8 '17 at 16:01
  • There is no mechanical reason to prevent the first and third digits being the same. (I too have owned a Master lock with a common 1st and 3rd digit.) The formula shows that the first and third numbers are both divisible modulo 4 with the same remainder due to the way the discs are made. – John Deters Nov 9 '17 at 0:53

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