If I find it again.   I didn't think to save it.  I only kept a copy of the Form which needs to be completed in duplicate and submitted to both the IRS and the Greek Social Security (IKA) Department.

(In 2017 I had enquired in person during my summer vacation, and was told that by submitting the IRS signed document at the beginning of each year, the amount of the Greek Social Security would not be shown on the E1 Tax Filing Document).