1 (1号機関車, Ichi-gō kikansha), is a British-built tank steam locomotive of 2-4-0T wheel arrangement, imported in 1871 by Meiji-era Japan for its first railway between Tokyo and Yokohama which opened in 1872.

This configuration was popular at the time in Britain, Europe, and elsewhere for locomotives that would haul either passengers or freight over short runs, and also for shunting.

For this line, ten locomotives of five different types were ordered in 1871 from builders in the United Kingdom, including one from Vulcan Foundry.

After being used between Shimbashi and Yokohama for about eight years, in November 1880 the locomotive was transferred to the Kobe area of what would later become the Tōkaidō Main Line.

1 was sent to Handa in Aichi Prefecture and used to transport construction materials for the Nakasendō trunk line project [ja] (which was later abandoned).

[3] On 1 April 1911, the locomotive was transferred to the private Shimabara Railway in Nagasaki Prefecture for the opening of their line; it was redesignated "No.

They installed metal clamp fittings on the front smokebox door, like those on U.S. locomotives, and replaced the steam dome cover with a crude cylindrical one.

At the beginning of the Shōwa era in the late 1920s, early railway journalist Kaizō Aoki [ja] started a campaign to return the valuable Locomotive No.

At that time, Shimabara Railway's founder and then-president, Gentarō Ueki [ja], in order to express his gratitude for the locomotive's contributions during the company's early days, had a plaque installed on the left side tank with the handwritten inscription, "With overwhelming feelings of farewell" (惜別感無量, Sekibetsu kanmuryō).

At one time, it had a steam dome cover taken from a JGR Class 5000 [ja] (an 0-4-2 tender locomotive of the same era), but this has since been removed.

In addition, the German-style sandbox and other items attached during the Shimabara Railway era have also been removed, and the locomotive has been restored to its pre-Shimabara form.

On 30 June 1997, it became the first railway vehicle to be designated by Japan as a national Important Cultural Property, under the Historical Materials category.

1 was moved to its current exhibition site, the present-day Railway Museum in Saitama which opened on 14 October 2007.