Greenwich observatory is one of the oldest, still functioning observatory, which is best known on the prime meridian passing through it, the zero degree of longitude.

The famous meridian can be found on several medals. One of these is a so called geocoin.  The geocoins - which are accessories of a new kind of technical hobby, geocaching - cover a wide range of topics. On the obverse we can find the meridian facing to Royal Observatory. The meridian continues vertically on the wall. In the legend around is the name of the observatory, Royal Observatory, Greenwich, below its geographical coordinates are shown. Longitude of the meridian is not exactly zero because Sir George Airy fixed the new zero point to the new instrument he made and set up in 1851, by which the old meridian was pushed by 5.79 meters to west. This difference is expressed by the small difference from zero.

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On the reverse of continuation of the meridian can be seen viewing from the building. Legend around is "Prime Meridian of the World,". The legend below and the letters in the image on the coin are part of geocaching, and are not belong to the subject of coin.

A medal issued in 1984 remembers about the centenary of 1884, when on the International Meridian Conference organized in Washington D. C., “the Conference proposes to the Governments here represented the adoption of the meridian passing through the center of the transit instrument at the Observatory of Greenwich as the initial meridian for longitude. (Ayes, 22; noes, 1; abstaining, 2.).” On the obverse of the gold-plated metal medal the map of the Earth crossed by the zero longitude can be seen. Legend around "LONGITUDE ZERO" and "1884 GREENWICH 1984" are the aforementioned two year numbers.

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On the reverse of the coin – as on the previous one – the housing of the passage telescope can be seen but here all the doors and the roof opened, in measuring ready state. Legend around is "PRIME MERIDIAN OF THE WORLD", below "EAST WEST".

The Flamsteed House, built in 1675 - the original, old observatory building - appears on the obverse of the following proof silver medal in half-side view.  Legend around is: "THE ROYAL OBSERVATORY," and at the bottom: "NAVIGATIONAL RESEARCH". The latter refers to the fact that the founder, King Charles II of England established the institution to carry out astronomical observations necessary to marine navigation. The king also established the Astronomer Royal  position for which John Flamsteed was named first. The designer of the building was the architect and astronomer Sir Christopher Wren.

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On the reverse in six lines the short story of the foundation of the building can be read: "Flamsteed House, Greenwich, built 1675. First government research establisment founded for perfecting Navigation and Astronomy.".

There is no longer going scientific research in Greenwich. The light pollution makes observation impossible for the urban observatories. The observatory now operates as a museum. Of it, and the foundation of the observatory commemorates a gilt medal, which was issued in 1975 at the tricentennial anniversary of foundation. On the obverse we can see the front view of the Flamsteed House. Behind it is the Earth's geographic coordinate network. Legend around is: "NATIONAL MARITIME MUSEUM" which indicates the current function of the building. Below: "GREENWICH HERSTMONCEUX", the latter name is the town where the observatory was relocated after World War II from where the observations were moved to the Canary Islands finally in 1998. Horizontally at the bottom the "ROYAL OBSERVATORY 1675 - 1975" legend appears, a reference to the tercentenary.

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On the reverse we see the chronometer H1 of watchmaker John Harrison, which can be found in the museum. The history of the famous watch appears in novelistic form in Dava Sobel's book: The Longitude. Summary of the story can be found on the museum's website, along with a photograph of the watch. The inscription is a quote from the order of observatory founder King Charles II: "Whereas, in order to the finding out of the longtitude of places for perfecting navigation and astronomy, we have resolved to build a small observatory within Our Park at Greenwich...", The italics are written on the reverse of the medal.

On the obverse of the next medal the Flamsteed House is placed half-rear view.

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On the reverse the museum's another building the "THE QUEEN'S HOUSE" is displayed. This medal is available in the museum's gift shop today.

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On another a coin appears the observatory building, i. e. the Flamsteed House. On the reverse of a medal that was issued in the occasion of the return of Halley's comet in 1986 shows it. Here you can see a comet over the observatory.