2 of the 30 International Meter Prototypes made for countries which signed the 1875 Meter convention. These were literally the definition of a meter. If they changed the meter changed. A few survive in national vaults, not all are accounted for. [4232×2781]

I have tried making a list of the 30 meter prototypes and find where they all went but I have had limited success. Certainly Japan, the US, Russia, and several others still show theirs.

There are 22 countries which signed the meter convention before 1900, presumably all of them were given one of the 30 bars.

Argentina,

Austria-Hungary,

Belgium,

Brazil,

Denmark,

France, (Bar No. 6 was kept as the BIPM standard in Paris)

German Empire,

Italy,

Peru,

Portugal,

Russia,

Spain,

Sweden and Norway,

Switzerland,

Ottoman Empire (became Turkey),

United States, (Received no.27 – https://www.nist.gov/image/meter-bar-27)

Venezuela,

United Kingdom

Romania (possibly inherited Austria-Hungary’s?)

India

Mexico

Japan (Received No. 22 – https://sj.jst.go.jp/stories/2025/s0624-01p.html)

Until 1960, if you wanted to know if something was a meter long, you compared it with this. It was a physical object which defined the length. There were also prototype weights made for the kilogram.

It’s not clear what happened to Meter Prototypes given to many countries, for example the ones given to Peru, Brazil, Spain, Italy, France, and Germany all went through one or more civil wars and could have been lost.

Related post with someone else who tracked down a few others:
https://hsm.stackexchange.com/questions/5141/what-happened-to-the-meter-bars

The bar numbers are listed in the original french here: https://www.bipm.org/en/committees/cg/cgpm/1-1889/resolution-

The meter is nowadays defined by the speed of light in vacuum, which is an universal constant, and time, which can be measured with extreme high accuracy.

“literally”