They paid a below-estimate £5000 for the bell from SMS Grosser Kurfürst (Great Elector), which bombarded Hartlepool in 1914, also fought at Jutland in 1916 and at the end of the war was interned at Scapa Flow but scuttled with the rest of the German fleet in 1919.
It was bought at the Atlantic Crossing Auctions sale in Southampton on March 22-23 and will be going into the new HMS Hear My Story Galleries at the NMRN in the coming months. The galleries recall 100 years of the RN from 1914-2014 and include a special First World War exhibition entitled Racing to War, the Royal Navy and 1914.
For many years the bell lay almost forgotten in a Bristol garden, after the ship itself had been salvaged but broken up at Rosyth in 1938, and it was bought then by the present vendor.
The NMRN said: "We had heard about the bell, but the article in the ATG was a very timely reminder. We had a buyer in the room - the director general heroically volunteered to go and bid in person."
The NMRN have been very busy at auction it seems. At Nicholas Mellors' sale on February 27 they paid £2600 (estimate £2500-4000) for a bronze portrait bust of Sir Philip Watts after being tipped off by the saleroom that it was coming up. Sir Philip (1846-1926) was a British naval architect, famous for his design of the revolutionary Elswick cruiser and HMS Dreadnought.
In 1905 First Sea Lord John Fisher's Committee on Designs in London was already thrashing out the plans that would overhaul the RN. Fisher assembled a committee of distinguished seasoned naval officers and eminent civilian scientists and industrialists such as Sir Philip, who became director of naval construction at The Royal Ship Yards at Portsmouth. Sir Philip went on to be instrumental in saving HMS Victory in the 1920s (now owned by the NMRN).
The sculpture, 5ft 4in (1.62m) high overall including marble base and oak plinth, with bronze 2ft 3in (69cm) high, is dated 1927. It was created by John Angel (1881-1960), a British-born sculptor.
NMRN director general, Prof Dominic Tweddle, said: "For other reasons we have bought two pictures from Bonhams recently; one of them of HMS Pique by Thomas Schetky. Pique ran into a rock off Newfoundland with the returning Governor General of Canada on board. The ship then sailed home with the rock stuck in it. The rock was then removed and can still be seen in the Dockyard. Our painting was one of a pair commissioned by the Governor General. The pendant is at Sandringham.
"The other picture is by Charles Wylie entitled The Dying Giant. It depicts a three-decker being broken up. We have identified the ship as HMS Albion. For us it tells the story of the transition from sail to steam, and wood to iron."
Both pictures came from the October 2, 2013, Marine Sale and sold for £22,000 each.