German bi-conical bottle from the 15th or 16th century – estimate €14,000-18,000 at Dr Fischer.

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The vessels comprised of two conical forms, merged together and are known today, not surprisingly, as bi-conical bottles. While they were unknown in Italy, they were produced in several regions in Germany, in eastern France, Czechoslovakia and as far south as the Balkans.

All the more surprising is the fact that no one knows where they actually originated and above all what their purpose was.

Many international museums, from the Metropolitan Museum in New York to the Budapest Museum of Fine Arts, own bi-conical bottles.

On October 29, collectors have the opportunity to buy their own so-called Stauchflasche (compressed or squashed bottle) at Dr Fischer in Heilbronn.

The 6in (16cm) high, yellowy-green German bottle from the 15th or 16th century, which has belonged to a south German collector since 1985, has a guide of €14,000-18,000.