​The most amazing things do turn up in local attics – but an exquisitely carved cup caused even Craig Bewick's  jaw to drop. The Journal antiques columnist and Brown & Co auctioneer reveals all . . .

This 17th century Chinese rhinoceros horn libation cup is expected to make at least £20,000 to £30,000 when it goes under the hammer at the Spring Fine Art and Antiques Auction in Brigg on March 27th

It may at first sight not look like it, but the extraordinary drinking vessel that we feature this month is quite simply the most valuable individual decorative object we have ever show in the column.

It is a 17th century Chinese rhinoceros horn libation cup. It is expected to make a minimum of  £20,000 to £30,000 when it goes under the hammer later in the month – and it may do considerably better than that.

Rather unbelievably, it has spent more than a quarter of a century in the attic of a local house, consigned to storage after a valuer from one of the major London auction houses took a look at it and dismissed it as being of little interest and worth only a few hundred pounds. More of that later.

So what an earth is so special about this piece? Well, it is very old, it is very rare, it is quite exquisitely carved and it is an extremely desirable object in a country (China) that now has people with the cash to acquire their historic works of art.

Libation cups are communal drinking vessels that were used in the upper echelons of Chinese society at great ceremonial events. They were created with various materials, including jade  – and rhinoceros horn.

This cup is carved from a single rhinoceros horn and it is a very, very fine example both in terms of its size (15.5 centimetres high, including the base, by 16 centimetres wide, at the maximum) and the quality of the carving.

Rhinoceros horn is a difficult material to work, but the craftsman who carved this went for glory. The quality of his work is superb and he has been bold, covering the piece with incredibly detailed scenes from 17th century Chinese life – and cutting deep into the horn to leave parts that stand clear of the main body of the piece.

The carving even extends over the lip into the interior of the vessel at one point, which is very unusual. In short, it is a real tour-de-force.

Sadly, the craftsman will forever remain anonymous; there is no maker’s mark. It would have been wonderful to know his name and that would have had a significant impact on the value. With a maker’s mark we would almost certainly have been looking at a valuation of in excess of £100,000.

The provenance of the cup is that it was bought in China and brought to this country between the first and second world wars by the grandfather of the present owners; it has remained in the family ever since.

They did consider selling it 30 years ago, but as I mentioned earlier, when they took it along to be valued by someone at one of the top London auction houses, he was dismissive. There was not very much interest in this sort of thing, he said, and if it went up for auction it would probably make £500 to £800.

Actually he was right. Thirty years ago there was not a huge amount of interest in Chinese rhinoceros libation cups but, as the modern valuation indicates, things have rather changed since then. A slightly larger example sold at auction at Christies last year for £103,000.

Discouraged by the pessimistic valuation, the owners decided not to bother selling and the cup went up into the loft, which is where it stayed until a few months ago when they decided to bring it in to one of the regular Thursday morning valuation sessions at the Brigg Rooms.

I have to admit its appearance from a small cardboard box was a rather exciting moment. It is the first example that I have seen outside a museum.

The good news about libation cups is that we are not plagued with modern fakes. Rhinoceros horn is today such a rare and valuable commodity in eastern societies . . . because of its supposed qualities as an aphrodisiac, that if you had a horn there would simply be no financial advantage in creating a libation cup. A resin copy would be a waste of time because it would be so obvious that it would fool nobody.

Our specialist adviser, one of the top experts in the country in terms of Chinese art, thought it was a fantastic piece and he was able to date it to the 17th century, so it could be Ming Dynasty (1368-1644) or it could be Qing Dynasty (1644-1911).

The cup is to go under the hammer at the Spring Fine Art and Antiques Auction in Brigg on March 27th, when it is expected to attract a huge amount of interest, particularly from and on behalf of the Chinese market. The auction is live on the Internet so collectors will actually be able to join the bidding from China, although it has been suggested the piece is so good that there may be people who fly in to be present in the room.

Amazing what turns up in local attics is it not?