Calcedonia glass turtle made by Murano master Dino Rosin, estimate £2000-2500 at Keys.

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Measuring 19 x 14in (48 x 35cm) it has an estimate of £2000-2500.

Born in 1948, Rosin learned glassmaking as his brother Loredano’s assistant and opened his own studio in 1992.

The Calcedonia technique that echoes the multi-coloured strata of zoned agate was developed on Murano in the 15th century.

Its secrets (the result of silver reacting with minerals and other substances in the glass) were thought to have been lost with the fall of the Venetian Republic but were rediscovered by Lorenzo Radi in 1856.