Russell Crowe's 'Art of Divorce' auction has raised $3.7 million.

The 'Gladiator' star marked his 54th birthday on Saturday (07.04.18) by staging a huge auction of his belongings, including artwork, 28 watches, and movie memorabilia and was thrilled by the result - especially as he was able to keep hold of some of the items he ''didn't really want to sell''.

He tweeted after the sale in Sydney: ''In case anyone is interested ... $3.7m at the coal face and around $350k of conversations ongoing ... and a bunch of stuff I didn't really want to sell coming home ... not a bad hourly rate for a 5 hour shift . Hope you are happy and busy (sic)''

A number of unusual items went to high bidders, with a jockstrap worn by the actor on 'Cinderella Man' selling for $7,000, despite an estimated price tag of $500-$600.

A dinosaur skull the 'Les Miserables' star bought from Leonardo DiCaprio fetched $65,000, while a pair of 18th century duelling pistols went for $26,000 and a bronze warship cannon sold for $20,000.

The famous breastplate worn by Russell in 'Gladiator' sold for a whopping $125,000, while its matching wrist cuffs sold for $32,000, a wooden sword for $20,000 and a metal one for $70,000, $5,000 more than a chariot from the film.

A range of Australian artwork also attracted high price tags, with various paintings selling for between $70,000 and $360,000.

Russell made a surprise appearance at the auction, appearing on stage after a rendition of 'Happy Birthday' and subsequent three cheers.

He then urged bidders wanting to buy an 1890 violin used in 2003 drama 'Master and Commander' to ''lend it to a young musician so it carries on and starts to play in the concert halls around the world.''

The instrument - which ultimately sold for $135,000 was then used by Australian Youth Orchestra member Bridget O'Donnell, who played two pieces from the movie, accompanied on the cello by Hanna Oblikov.

Russell - whose divorce from Danielle Spencer was finalised last year, five years after they split - previously admitted he'd had ''fun'' putting together the auction of over 200 items.

The 'Nice Guys' star - who has sons Charles, 14, and Tennyson, 11, with his ex-wife - said: ''Getting to this point with the divorce, and no matter how amicable a split is, you've still got to unwind things at a very deep level. I've never been someone who deconstructs things, I've always been someone who builds things, so it was quite a big lesson in life to become someone in life who can deconstruct things.

''I thought to myself, while I'm in the middle of doing that, how else can I do that? How else can I apply that. This is what I came up with.

''Actually it's been a lot of fun, this is almost like doing a full production. It's taken me 12 months, choosing the articles and how they balance with each other.

''It's been joyful. I'm kind of excited to see what happens.''