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. Brass crank winding key made for H3 in 1931 as part of Gould’s restoration. The key is engraved: 'HARRISON No.3 1931'.
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National Maritime Museum

. Four brass support pillars, made in 1930 when H3 was being fitted into its first showcase, and transferred to the new showcase for the NMM display in 1936. All three large timekeepers remained in these 1936 showcases until 1984 when they were transferre

National Maritime Museum

. The front cap of H3’s caged roller bearing, removed for many years to enable the bearing to be observed on display.
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National Maritime Museum

. The glazed brass case of H3. The case is constructed from thin brass sheets, all pieces are carefully fabricated using coppersmiths dovetailed joints down the edges and silver-soldered, a highly skilled exercise on a piece as large as this. The thin gla

National Maritime Museum

. The rear cap of H3’s caged roller bearing removed for display. In the poor conditions at sea it was important to protect this very sensitive part from the ingress of dirt and dust and Harrison designed it to be virtually sealed with these caps.
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National Maritime Museum

Grasshopper pallet. Glass tube containing one of H3’s original oak pallets. The pallet nib end is missing and the pallet now has an experimental metal (zinc?) nib, made by Gould, clamped to it, as well as a small lead counterweight bound to the pall
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National Maritime Museum

H3. Marine timekeeper, H3. Started in 1740, this third timekeeper took Harrison nearly 19 years to build and adjust, although it was not to win him the great longitude prize: he found that he just could not persuade the two large, heavy, circular balances
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National Maritime Museum