I am impressed that you kept records of what you paid for a coin you bought 44 years ago. Does everybody else keep such detailed records? Very nice coin by the way!
My father gave this to me. He has record books of every coin he has ever bought/sold, the price paid/sold, who he bought from/sold to, and stickers on the back of each slab with price paid, year bought, and who he bought from.
I can pretty much tell you when, who and how much I paid over 50 years I've collected. Some written records... but mostly recall.