Silver In Guatemalan Circulation?

The fact that coins are demonetized means they are no longer classified as money in their country of origin. It does not mean that in 1996 or earlier that silver coins were actually in circulation.

It is like Kennedy half dollars in the US - they are all still monetized meaning they can be spent or redeemed. The coins from 1964 are 90% silver while others dated before 1970 are 40% silver and later coins are copper nickel. The silver coins were removed from circulation in the 1960s for the most part. But if you are ill-informed you could still spend a 1964 half dollar as 50 cents instead of selling at as silver for over $6. The 40% coins do appear in circulation but those are rare events.

So like most places on earth it is unlikely that Guatemalan silver coins remained in circulation after 1964.