The entries in LocalSet consist of key values related to key indices in Symbol, and three additional attributes, the key values for route, unit of currency, and variant part tag index.
The first two are straight-forward, and have already been encountered in a different context, as symbol home exchanges, and currencies to be traded. Here the route refers to the floor or ECN where the trade is to take place or cross, while the currency is used as a unit of denomination.
The tag index varies in interpretation with the security type, and as it implies additional variant part data such as expiry and right. For stocks and indices, where there is no variant part, the tag is always zero, while for futures and options it stands for a tuple index into either of the tables FutDetail and OptDetail.