I recently bought EOD data stretching back to 2006 on an option series from CBOE. Frankly, the data is a disgrace and I got no reply from my complaint to CBOE.
Problems include strike prices out by up to 3 decimal points in some cases and phantom expiration months which suddenly appear and equally suddenly disappear.
I am having to go through the data line by line to correct the errors. Any attempt to perform systematised analysis on the data I bought was a farce before the tedious hand conducted clean up.
I also have a problem with the expiration dates. There is no trading on the day of expiration – instead the 0’s are shown for each strike. It seems absurd that the exercise-settlement value is not stated and there is no way to calculate or approximate it since the data does not even include the day’s spot opening price for the VIX.
Unless I have badly misinterpreted something (always possible) I would say shame on the CBOE for selling such misleading data. Its value for my purpose is rendered almost useless.