Imperial Personal Identification Number

• I'm currently designing a set of Traveller identity cards to be used as props and/or NPC cards in our games. One of the features I cannot imagine any kind of post-industrial society without some kind of serial number displayed on identity cards. Not wanting to make it entirely random, nor wanting to invent a new system for every Traveller organisation, I'm going with a "universal" Imperial Personal Identification Number (IPIN) that's use by most imperial and local organisations.
• Because of the lack of FTL comms in Traveller, such a number would have to be attributed locally (out of a preassigned block) and then transmitted to central databases. So here's my take at it.

System - Date of Birth - Serial Number - Checksum

• System: a unique identifier for each issuing planet. I'll just go with a number for the sector followed by the hexagon number of the system. The easiest way would probably be to go with two letters for each sector, like "SM" for Spinward Marches, but that would make the checksum mechanism too complicate for my taste, so 2 digits it is. Not a very efficient scheme, 7 digits to code the  9000ish systems of the imperium; but one that present the advantage of using information readily available to any GM.

TTL5/GTL6 cogs of bureaucracy. In one of my very favourite movies of all time!

• Date of Birth: YYYY-DDD, the standard imperial date system with the year up front.
• Serial Number: a number unique to each individual born on a given day in a given system. Now the most populous system in Traveller (population code "B") can have 1 trillion (10^12) inhabitants. Give them an arbitrary life expectancy of 27 years and you got an average of 100 millions (10^8) births each day. Note that the higher the life expectancy is, the lower the birth rate needs to be to sustain a given population. Even taking into account "seasonal" variation in the birth rate, 9 digits should be amply enough to unambiguously code anyone. The defaut mechanism to assign those is sequence of birth. But balkanized systems, or ones too lowtech to maintain a single readily accessible central database might need to further split that serial numbers in blocks assigned to political entities or census subdivisions. A noteworthy side effect is that a sophon born, let's say, on a Pop 6 world will probably have "0" for the 6 or 7 first digit of this block.

• Cheksum: not my forte and there are probably smarter ways to do it, but let's start with the modulo 997 of the rest of the IPIN. If you happen to have ideas of better ideas to do it, please let me know!
• Bottom line: a whoping 25 digits! 

 SSHHHH-YYYYDDD-PPPPPPPPP-CCC