19th century diving helmet, possibly by John Date or Siebe Gorman, $45,000 (£25,500) at Nation’s Attic.

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This helmet carries no identifying marks but dates from the 1860s or 1870s – just a matter of decades after the German instrument-maker Augustus Siebe issued his ‘Siebe Improved Diving Dress’ in 1840.

The skilful soldering of copper and the use of convex glass suggests it was the creation of diving pioneer John Date in Montreal or possibly the Siebe Gorman firm in London.

The late collector had found the helmet with a stash of other vintage diving equipment in North Carolina. He purchased the entire lot decades ago, and the helmet was never shown or shared with the diving community.

When the lot came up for bidding, it immediately jumped above its $10,000-20,000 estimate and kept climbing until it hammered at $45,000 (£35,500) to a bidder using LiveAuctioneers.

Date, a master coppersmith and brass founder, established his workshop in 1853 making most of his helmets to order.