In order to filter out already expired options, I was reading the iqfeed guide to options symbols:https://iqfeed.net/symbolguide/index.cfm?symbolguide=guide&displayaction=support§ion=guide&web=iqfeed&guide=options&web=IQFeed&type=stock
From what I understand, the letters before the first digits in the symbols represent the underlying. Then comes the info on the expiration data, with the first two digits representing the year, then 2 digits for the day and a letter for the month code. Then there are digits represnting the strike.
So a code like CSCO1220V19 means Cisco October Put at 19.00 Expiring on 10/20/12
But why other symbols, like A11720A27.5, representing Agilent Call 20 expiring on Jan 20 2017 have an extra digit ('1') after the 'A' symbol? It doesn't make any sense.