The Pink Panther star originally decided to leave his youngest daughter Victoria just $1,200 (£800) of his fortune - but changed his mind in early 1980 and tried to increase the amount to $30,000 (£20,000).
The funnyman suffered a heart attack and died on 24 July, 1980 before the changes could be made to legal documents.
Now Sellers' doomed request is to be auctioned off - along with the actor's Golden Globe trophy for 1979's Being There - at an auction in Wiltshire, England on Saturday (17Jul10).
A source tells Britain's Daily Express, "Had Victoria received the bigger sum that Peter had granted her she'd have had the kind of financial security for a better start to her adult life. Peter made a real mess of his financial affairs and Victoria and his other children suffered the consequences. It's tragic to think he came so close to changing things for the better, only for it to be too late."
Victoria, whose mum was Bond girl Britt Ekland, led a troubled life after her father's passing - she posed nude in Playboy magazine and made a sex tape with Hollywood madam Heidi Fleiss. She was also jailed for drug crimes.