France 100 francs, what is the difference?

I got some silver 100 Francs at an auction, and I am in the process of identifying the catalogue numbers. These are 1980's 1990's .900 silver commemorative coins, but what is the difference between circulating and non circulating, e.g KM#970 and KM#970a? Same with other years.
Here is one of the coins

(Please include Numista links when you talk about a listed item.)

KM# 970: https://en.numista.com/catalogue/pieces32.html
KM#970a: https://en.numista.com/catalogue/pieces20804.html

According to Numista the difference is the thickness and the strike (970a is proof).
According to Krause the difference is the purity (which would affect thickness, but not as much as shown in Numisa listings) and the strike.
Gadoury uses the same type number for both.

Cita: "bjherbison"​(Please include Numista links when you talk about a listed item.)
​
​KM# 970: https://en.numista.com/catalogue/pieces32.html
​KM#970a: https://en.numista.com/catalogue/pieces20804.html
​
​According to Numista the difference is the thickness and the strike (970a is proof).
​According to Krause the difference is the purity (which would affect thickness, but not as much as shown in Numisa listings) and the strike.
​Gadoury uses the same type number for both.

​Strange how the thickness of one is nearly 50% more than the other, but diameter and weight are the same. I wonder if the weight is wrong on that example? All the ones I got are 15g.

Is it really possible for a 15 g. silver coin issued in 1989 to be "circulating"?

I think not.

As for the dimension question, it is only possible to have same wight at different thickness in this case, if there is a large difference in relief.

I think there may be room for some corrections?

KM# 970 is a business strike and they have been issued at face value.
KM# 970a is a proof coin and has been sold with a premium.

Cita: "maudry"​KM# 970 is a business strike and they have been issued at face value.
​KM# 970a is a proof coin and has been sold with a premium.
​

​I get that bit, we still have proof and uncirculated coins in the UK, also non circulating issues which sometimes get into circulation, often referred to as NIFC (found that out on those coin hunting YouTube videos). What I'm trying to find out is if there is any distinguishing feature between the two, and would anyone be able to tell if the one I posted a picture of is proof or not? Bearing in mind the coin was in a tin with all the other 100 franc coins I got.

Look at the images in the two links I posted and compare the surfaces of the coins. Then compare them with your coin.

KM# 970: https://en.numista.com/catalogue/pieces32.html
KM#970a: https://en.numista.com/catalogue/pieces20804.html

Cita: "tdziemia"​Is it really possible for a 15 g. silver coin issued in 1989 to be "circulating"?
​​I think not.

​They were actually circulating and you may find some with scratches in flea markets. At that time 100F was expensive
Same as the 5 Francs silver 12g in the 60's

And for this 100F 1989 coin, the silver purity is not the same between the different issues

Cita: "tdziemia"​ As for the dimension question, it is only possible to have same wight at different thickness in this case, if there is a large difference in relief.

Your right, perhaps a confusion with "Piedfort"

Cita: "bjherbison"​Look at the images in the two links I posted and compare the surfaces of the coins. Then compare them with your coin.
​
​KM# 970: https://en.numista.com/catalogue/pieces32.html
​KM#970a: https://en.numista.com/catalogue/pieces20804.html​

​For people who are not familiar with proof coins I think the pictures in the second link or not the best to compare.
I think these are better to show the difference:



For the OP: as you can see the proof coins have mirrorlike fields and frosted images. On your coin you can see there's no difference between the fields and the images or lettering. So yours is the non-proof KM# 970.

It could circulate as in 1989, silver was around $3.50 USD an ounce which was around 15 - 20 Francs. The coin only had .38 an ounce of silver or around $1.25 worth, the face value of 100 Francs was around $20 USD, so it would be worth metal wise, way below face value.

When I first started buying silver coins in 1991, I remember you could buy American melt silver at like $5 USD an ounce and I got everything except Dollars that cheap. I remember buying old Walkers and Frankies at like $3.50 NZD each. In 1991 a NZD was worth around 55 US cents.