French Indochina

Everyone knows and probably loves- the French Indochina issues of 1885-1937/8.
I recently obtained the following FI coins:
1938 1/2 cent VF
1892 1 cent VG
1937 10 cents AU
1909 1 Piastre VF

If you have those coins (except the 1/2 cent), you will have noticed the iconic 'tailed liberty'  reverse of the coins. The tail is actually an anchor propped up behind the liberty figure, but what i really want to talk about in these coins is on the obverse, you can see the weight, I presume- of the coin. On the cent, it says: POIDS 10 GR, On the 1937 10 cents it says: TITRE 0.680 POIDS 2gr 7, and on the Piastre it says: TITRE 0.900. POIDS 27 GR.
To my best French knowledge, POIDS means pounds, and I assume that GR means grams.
I have not seen other coins with such exact weights on the coin itself before, and would like to know why this was.

Verweis : BrittaniaI have not seen other coins with such exact weights on the coin itself before, and would like to know why this was.

Check out German states coins. They often have phrases like "XXX EIN PFUND FEIN" (30 in a metric pound).

Back in the day, when Annam and China used Tael-based coinage, the only silver that circulated was European silver. Therefore, the dimensions were used to relate the values of unofficial "coinage" (silver ingots). Also it's simply a measure of anti-counterfeiting.

Hey, if you want some Indochinese coins, I got some. A modified date 20 cents and some zinc cents where the date wore off. Let me know if you want them.

  There are three 1800s Spain coins with the weight on them. When I first saw one I wondered what currency Gramos was (as no country on the coin), then realised it was the weight.
 There is 2 or 5 or 10 Centimos, e.g. ...

https://en.numista.com/catalogue/pieces4242.html

So does Mexico older silver. And most of South America