Best way to farm Unsealed letter

How this is calculated: items/hr = (3600 ÷ seconds per kill) × average items per kill. Each monster's drop lines are listed as the wiki shows them (rarity · quantity); the average adds them all up, each as rarity × average quantity × rolls — so a guaranteed drop plus a rarer bonus drop both count. Drop rates and quantities come from the OSRS Wiki's community-verified drop tables. Seconds-per-kill is an editable estimate based on each monster's hitpoints and defence — your real speed depends on your stats and gear, so adjust it and your edits are remembered on this device. Rates marked ~ are approximate on the wiki.