> imo=9811000 I find it neat? strange? that IMO numbers have checksums: > An IMO number is made of the three letters "IMO" followed by a seven-digit number. T

> imo=9811000 I find it neat? strange? that IMO numbers have checksums: > An IMO number is made of the three letters "IMO" followed by a seven-digit number. This consists of a six-digit sequential unique number followed by a check digit. The integrity of an IMO number can be verified using its check digit. This is done by multiplying each of the first six digits by a factor of 2 to 7 corresponding to their position from right to left. The rightmost digit of this sum is the check digit. For example, for IMO 9074729: (9×7) + (0×6) + (7×5) + (4×4) + (7×3) + (2×2) = 139.[10][11] * https://en.wikipedia.org/wiki/IMO_number#Structure https://en.wikipedia.org/wiki/IMO_number#Structure MMSI numbers do not: * https://en.wikipedia.org/wiki/Maritime_Mobile_Service_Identity https://en.wikipedia.org/wiki/Maritime_Mobile_Service_Identi...