W Mint Quarter Die Pairs

I think there is two die pairs per design.

I think Oldfordman is likely right, however, you could try a FOIA request and see if they have the information on that to be sure. They should be accounting for how many pairs were made, maybe not used, but made.

I know West Point uses a vertical Graebener GMP 360 TK presses, it's a single piston press, No idea on how many coins they get out of a die pair though but I could see them just running the one machine to do the 2 million strikes. it's not exceptionally high speed, so I think in theory an operator could do all 2 million off the one die pair as long as he's watching for die problems along the way and have the 2nd pair for a backup, maybe switch to the 2nd pair halfway through, and go back to the 1st pair if the 2nd pair gets messed up too bad.....

two pairs is plausible, one pair is not really because of no back up, and I think 4 pairs would probably be overkill for business strikes on that machine.

For Denver and Philadelphia die life before they went to the horizontal presses was about 750,000 coins per die pair (not sure what the die life is now.) So I would expect about 4 die pairs per design. Doing the whole run on a single press would take about 13 days running 24/7.