The hack is reducing the experience to level by 10 and the gold to purchase items by 10. DW1 Mass Data Editor was used for this change.

To use the old tool DW1 Mass Data Editor, DosBox was used, mounted a folder and put the files dragonw1.nes, DW1MDE.EXE and CWSDPMI.EXE inside the folder. Run the DW1 Mass Data Editor.

DW1 Mass Data Editor https://www.romhacking.net/utilities/62/

DosBox https://www.dosbox.com/

csdpmi5b (CWSDPMI.EXE) https://www.dosgamesarchive.com/file/nethack/csdpmi5b/