I have been in the US for over 2 years, and in that time I have noticed that coins minted before the mid 90's are of substantially higher quality than those minted subsequently. The old coins appear to be more '3 dimensional', and details are much finer. The difference is such that if you gave a person in the 1970's a recent coin but with a date from the 70's, I suspect it would be outed as counterfeit.
Conveniently, I have a decent camera with nice prime lens and manual focus, and can show a couple of examples.
First, let's compare a 1961 penny to a 2013 penny (by the way, I dislike pennies and think their continued production is exemplary of much that is wrong with the US government, but that's another issue).
The 1961 penny pictured below was received as change. It has been in circulation some 52 years and has bits of black crud stuck to it. It's an alloy of 95% copper, 5% tin and zinc. Observe the depth of the writing, and the very clear depth of the Lincoln bust.
Now let's look at a 2013 penny (below). It's a 99.2% zinc + 0.8% copper alloy blank, plated with 100% copper, resulting in a final composition of 97.5% zinc + 2.5% copper.
Comparing the two, I might think "Did I mess this photo up?" Apparently not, as you can see the very very tiny shadows cast by Lincoln's almost completely insubstantial bust, and that the bottom half of the coin is clearly in focus.
OK, so we all know that pennies are worthless, and that modern ones are basically copper plated chum. Perhaps the mint is cheaping-out on them, knowing that most of them are immediately thrown away.
How about Kennedy half-dollars? Below is an image of a 1971 Kennedy half-dollar. Note the pleasing depth of the US Great Seal.
To compare, below is a 2000 Kennedy half-dollar.
Yuck... What... Is... That? Yes, I know the 2000 coin is more worn because the milling is worn down, but the strike never had any depth to begin with. I also have a 1983 coin that resembles the 1971 coin.
It's not just these coins either. Quarters, nickels, and dimes also consistently show the same features. I don't have any to hand, but this effect can be very frequently seen, especially in quarters.
So why the apparent decrease in the quality of US coins? If anyone who knows how the US mint operates can comment, it would be nice to know what actually happened. Is this a cost cutting measure? Was it a design fad?
P.S. If anyone wants to know why I care about these things, it's because my parents gave me one of these:
It's not really worth anything beyond its silver bullion value, but it's a beautifully designed and made coin.