I was looking at some ancient Greek coins (ca. 200 BC), and was struck by the high quality of the coins-the images of the portraits were sharp and well-defined. Were steel dies used to strike these coints? And, how did the ancient engravers (without power tools) make such sharp, well-defined images (in reverse)?
How long would these dies have lasted? And, were powered (watermills?) hammers used to strike ancient coins, or was it done by hand?
I know we have a numismatist on the dope, but let me chime in -
The die sets were carven by hand, by engravers - and they were able to do quite fine work. Gold, silver and bronze are relatively soft metals, and stamp fairly well with iron or steel dies.
Just because it was 2000 years ago does not mean that people were not able to do quite fine work, in fact several metalworking techniques were developed and then lost until recently [granulation, and true wootz steel specifically] 
This isn’t my field of expertise, but I’ve read that they would first create a rough iron die, which they would then anneal to harden it. After it was hardened, a skilled craftsman would add all of the fine details using hand tools (sorry, I don’t know exactly what tools they used). When they struck the coins, one man would heat up the blanks to soften them and then would place them on the die. The second man would then whack it with a hammer to strike the coin. Because they heated up the metal to soften it they didn’t need to have hardened steel dies like what we use today.
Now obviously “ancient times” covers a whole lot of time and a whole lot of different places, and techniques varied a bit, but I’ve never heard of them using any sort of automated equipment like water wheel powered hammers.
“Anneal” = soften. The die would be rehardened once engraved.
Here’s a link to a fairly well-written article on what we think happened 2000 years ago.