Buffalo Nickel 1937-D 3 Legs

The die was polished excessively by a mint worker, destroying the low-relief elements of the design, including most of the one leg.

I don't know about intentional. The US Mint takes a great deal of pride in its work and quality control aspects. And this is a variety not an error.

Wouldnt that suggest that when these "mistake" coins come out that it is more likely to be intentional? At least for the more modern ones anyway.

If they did sloppy work you would see a lot of these. But like you said they take a lot of pride in their work and quality control which begs the question how so many different error type coins have gotten out. Even very recently as well with all their new technology and methods we still see some "error" coins coming out.

Im just speculating, but I know if I was in charge of the mint and I wanted to get interest going in a particular series or get collectors really excited about something I would put out some "errors" every now and then which will have added value

If you owned a company that made BILLIONS of products every year, what would your fault rate be? I bet it would be higher than that of the US Mint

It is also a matter of what you are referring to as "errors". Die varieties are not errors and with the advent of single squeeze hubbing, doubled dies would be much more difficult to identify before the affected die was put into production. Cracks, chips, and clash marks are an accepted part of the minting process so there is no reason to screen them out.

This is also the reason why we, as numismatists, should be humble about our hobby.

Many of our large-hitting rarities are screwups. :-)

I'd be pretty embarrassed if there was a market for all of the mistakes I've made over the years.

I agree with Conder.

A die state is one like this that changed with time -- an example would be die cracks.

A die variety would be a DDO, or a RPM

What most of us never see is just how many error type things are produced by all sorts of companies, every day. AND with the auto industry, the only errors you hear about is when someone gets killed or almost killed and then there is that famous recall thing. Companies like Sears, Kmart, Walmart, Best Buy and on and on and on sell STUFF every day that doesn't work. Which is why they all have those return policies. Of course they don't make that stuff but they do sell it to you and no one is really checking that stuff, or at least in China, that is.
I remember when Chrysler was famous for putting things on cars and waiting for the populace to either rave about it or try to have it removed. Anyone remember their famous pushbutton drive? That one almost cost me my legs.
The Mint is doing a decent job when you compare them with some of the other companies we deal with.
But do remember about M.E.S.S. too.

I know this is a coin forum but I had a 62 Chrysler with those. Was tuning it up in my garage, standing in front, main door closed, it jumped into drive. Remember those bullet type bumpers? They saved my legs.