A wig made for Elizabeth Taylor's 1963 film Cleopatra, but never worn by the star, is to sell at Bonhams LA on May 5. The British-made, human hair wig is believed to be worth $8,000-12,000.

The wig is one of several made for the film. As Bonhams does not believe the wig to be screen-worn, the estimate is lower than would otherwise be the case.

Two bamboo chairs used in the 1942 film Casablanca are also to feature in the much-anticipated sale. Estimated at between $4,000 and $6,000, the chairs were used in Rick's Cafe - the atmospheric piano bar and gambling den presided over by Humphrey Bogart's character Rick Blaine.

In December 2012, the piano from Casablanca sold for $602,500, reportedly to actor Leonardo DiCaprio. Although the piano is a much more iconic piece than the chairs, its sale suggests collectors are keen to acquire props from the film.

Further highlights include an expansive array of Marilyn Monroe memorabilia, movie posters and Dallas collectibles.

Among the Marilyn Monroe items on offer, a group of George Barris photographs valued at $5,000-7,000 and a Marilyn Monroe-inscribed copy of the Gentlemen Prefer Blondes novel, estimated at $3,000-5,000, are highlights.

The late, great, Larry Hagman's JR belt buckle

Dozens of hats worn by Larry Hagman, who played ruthless oil baron JR Ewing in the American TV series Dallas are expected to bring several thousand dollars, while Hagman's JR belt buckle is valued at $3,000-5,000.

We have an extensive array of investment grade memorabilia for sale, including this Marilyn Monroe autographed cheque.

Collections are often amassed for pleasure, not profit. Yet substantial price increases suggest we ought to think about collectibles in terms of investment, as well as enjoyment. For more information on the movie memorabilia market, see Paul Fraser Collectibles' free guide to investing in memorabilia.

Still haven't made your mind up? Check out these 10 great reasons to invest in collectibles today.