Many songs co-written by the pair were lost, says Sir Paul
U2 frontman described Lennon as being "one more Irish immigrant on an island full of Irish immigrants"
Collectible item sold at auction in Boston, USA
The item will go on sale at RR Auctions from July 16 to July 23
Alleged ISIS terrorist Mohammed Emwazi takes his nickname from John Lennon
Singer says his former Beatles bandmate did 'a lot of great work' but also 'a lot of not-great work'
Bidding for the postcard is currently at $12,636 (£8,000)
Production is set to be launched in April 2016
The 1968 album is said to have been a major influence on the US criminal
The item, relocated after 50 years, is expected to fetch between £400,000 and £500,000