Portuguese DTMN code
The four-digit code identifying a Portuguese municipality, assigned by INE and published in the official administrative map.
Two bodies are involved and they do different things. INE, the national statistics institute, assigns the code. The Direcao-Geral do Territorio publishes it together with the official boundaries in the Carta Administrativa Oficial de Portugal, which is where the values are usually read from.
Four digits: two for the district and two for the municipality within it. Abrantes is 1401 in the district of Santarem. There are 308 municipalities.
The leading zero is part of the code, and the autonomous regions sit in their own district block: Lagoa in the Algarve is 0806 while Lagoa on Sao Miguel in the Azores is 4201. A district table that stops at 18 loses the islands.
This code is the middle width of a longer scheme. Adding two digits for the parish gives the six-digit DICOFRE, so a four-digit and a six-digit value in the same column would be different kinds of unit rather than the same one.