Unless i didn't read it correctly, this article shows that Philadelphia and San Francisco don't do it the same way. Philadelphia Sandblasts the entire die to frost it, then masks off the frosted parts and then polishes around the masked off portion. San Francisco, on the other hand, polishes the entire die and then uses a laser to frost the desired parts. Does this different processing method show up as detectable differences on the coins themselves?
If you read all of the series of articles you'll see that the mints change the way they do things depending on the coins they are producing. And they not only change the sequence in which they do things, they also change the methods in which they do things. Everything we see in these articles is fairly recent, and it's great material. But the articles tell us just how much and how often things do change. And it's always been that way to one degree or another, the mint has always experimented with different methods and technology for all of the processes they go through to make coins. And it depends on what year(s) we are talking about as to what they did, how, and when. Even in the article you linked, it tells us that Philly was sandblasting to frost Proofs, but then it tells us that in 2013 (the current year when the article was written) that they switched over to lasers for frosting Proofs. But the truth is they switched over to lasers a long time ago. Just apparently not on all coins, and not at all mints. And they switch back and forth from one method to another. And they do and have used acid etching, sandblasting, and lasers, and varying methods of all 3 individual methods at that - just to frost Proofs. And as for polishing the dies, there have been changes in that too, but even in the 1800's they were using various grits of diamond dust paste to polish dies. And they were using machines to do it - not hand work. Of course they still use machines and diamond dust paste to polish dies today too. We just aren't seeing it in those articles, but you'll find it in other articles. And to answer one of your questions, yes, there are very distinct and easily noticed differences in the coins. Take the following pictures for example, they were posted here on the forum by another member about 5 years ago. Now it's pretty easy to see the differences and how they changed from one year to the next. And yet all of those were done with lasers. And if you look at the coins of today, they are even different than those. But those pictures do one thing quite well, they clearly illustrate that not all changes at the mint are for the better. For how can anyone say that the frost on the 2007-2010 coins is anywhere near equal that on the 2006 coins. And of course we must take into account that all of those pictures are of annual Proof Set coins. Which is important because other types of collector coins could have well been made differently, for each different kind of coin, and in different years. Bottom line, those articles are not representative of what and how it is done with all coins - just some of them. We need to keep that in mind.
