[David Lange] Note that the flyer carries a printed date of 189, with the final numeral to be entered by hand, a not unusual situation for legal or financial documents of the time. However, the text states that proof coins were being struck with a screw press. I believe that practice ended in 1893, when the screw-driven medal press was replaced with a hydraulic press for coining proofs. The flyer was most likely printed sometime between 1890-93, and a quantity of this document still remained on hand when the illustrated example was sent out in 1898. 

[Roger Burdette] The text appears to predate introduction of an hydraulic press for striking proofs. That is not unusual. The Mint often used forms internally and for external communication until the supply was exhausted. Records indicate they were parsimonious in using forms, copybooks, flyers and other materials. David Lange's comment is certainly accurate. I might further add that we do not know on what date the first proofs were made on the new hydraulic press, or if both old and new presses were used simultaneously. As most are aware, new equipment often requires a lengthy break-in period and considerable "learning-curve" for the operators.