Up to six firms are understood to have submitted bids for the company, including offers from the UK arm Mitt Romney-founded Bain Capital, as well as Pret-a-Manger owner Bridgepoint.
Boutique investment bank Greenhill is advising on the sale of the company.
The auction house has displayed impressive growth figures recently and posted a 32 per cent increase in hammer sales in 2013, helping deliver a doubling of operating profit to £25m.
Its reputation is staked on the auctions of high end goods, with lots including the Formula 1 racing car that drove to victory in the 1954 Swiss Grand Prix, which sold for £19.6m last year.
The business is owned by a former motor racing driver, Robert Brooks, alongside the heir to Holland’s famous Louwman Museum, Evert Louwman.