| I think the IRS understands your particular situation, and for your information, whenever there are multiple stock purchases made at various times of the year and over several years that date over 10 years I think you can use a best estimate method and document how you arrived at this amount in your file.
I would take the average price that ranges from 1988 to 2006 based on your stock shares purchased. An average cost price will suffice in this case. An attempt at your best estimate will be accepted by the IRS! | 
