The auction house added that Mr Belcher was unavailable for comment.
The centrepiece of the auction, the Faith guitar, is expected to fetch in excess of £100,000, with estimates ranging between £60,000 and £120,000.
A Filofax from the 1988 Faith tour containing Ms Bailey’s handwritten notes had already attracted a bid of £1,750, far surpassing its guide price of up to £600.
Among the other lots are a four-page running order from Live Aid in 1985 featuring Mr Michael’s duet with Sir Elton John, gold and platinum discs marking sales milestones, rare cassettes and acetate singles marked “Not For Sale,” and personally inscribed signed photographs.
The entire archive is anticipated to realise more than £200,000. Sworders chairman Guy Schooling previously said the sale would give fans worldwide the chance to own “pieces of music history.”