[frogjerk]

In 1889, the copies and the kilogram weighed the same, but by 1989, they had drifted apart. Based on the data, the kilogram appears to weigh slightly less than the copies.

Then use the copies.

[GonzoGOP]

Perhaps the copies are gaining weight. I know I have put on a few kilos since 1989. Perhaps the copies have been sitting in front of the tube watching Oprah and eating bon bons.

[MosesKnows]

Then use the copies

You miss the problem. When they differ how would you know which to use, the original or the copy? Did the copy become heavier or did the original become lighter?

Therein resides the dilemma and that is why they seek a solution.

[GeronL]

Then use the copies

*stupid french accent*. "Oh, dat iz eazy for you to zay. But ve are ruled by zee bureaucrats and zee treatiez. It izn't so zimple az dat. Dis iz zee law. Ve listen to zee law"