In the Philosophical Investigations §50, Wittgenstein writes:
There is one thing of which one can say neither that it is one metre long, nor that it is not one metre long, and that is the standard metre in Paris. – But this is, of course, not to ascribe any extraordinary property to it, but only to mark its peculiar role in the language-game of measuring with a metre-rule.
Suppose a child looks at the standard metre, not knowing what it was, points at it and asks his father how long it is, what should his father answer?
EDIT - a note about the paper by Pollock, referenced by @JosephWeissman in the comments:
In the paper Pollock criticizes Kripke:
Kripke certainly does not seem to understand how a standard is chosen for a measuring system when he suggests that the person who chose the standard for the metric system already knew what a metre was before he had chosen the standard for the system.
As Kripke puts it in Naming and Necessity, the person who performs such a ceremony is:
using this definition not to give the meaning of what he called the ‘meter’, but to fix the reference. (For such an abstract thing as a unit of length, the notion of reference may be unclear. But let’s suppose it’s clear enough for the present purposes). He uses it to fix a reference. There is a certain length which he wants to mark out. He marks it out by an accidental property, namely that there is a stick of that length
But it seems to me that Kripke correctly describes how the standard metre of Paris was created according to the Wikipedia:
While Méchain and Delambre were completing their survey, the commission had ordered a series of platinum bars to be made based on the provisional metre. When the final result was known, the bar whose length was closest to the meridional definition of the metre was selected and placed in the National Archives on 22 June 1799 as a permanent record of the result. This standard metre bar became known as the mètre des Archives.
Namely, the French committee chose the platinum bar which was accidentally closest to the length computed by the surveyors.