My first
BTC came from trading a protoplast of cryptocurency called calam coin,
on deutche forum/website service called clam.de. 10 years ago they created
a coins system for atracting crowd to their website, i have registered, used the site for a while
and forgot about it.
10 years later (2015) an email from clam.de apeared in my box, i have remambred the password

and to my amusement amout of clam coins was acumulating over the years.