Heartseeker Scope

This scope seems to be relatively much cheaper in mat cost to the stabilized eternium.

Tha beauty made my engineering skill from 449 to 450 thought it's listed in lower skill from Advanced Trade Skill addon than http://www.wowhead.com/?item=40772

I do not understand why the above comment was downrated. The chance to gain a skillup from a yellow or green recipe is (gray level - current skill level) / (gray level - yellow level). This recipe goes yellow at 435 and gray at 455; the Gnomish Army Knife goes yellow at 440 and gray at 450. At 440, this has a 75% chance to increase your skill whereas the knife has a 100% chance. However, the knife's chance drops off twice as quickly. At 445, they both have a 50% chance. After 445, this has a higher chance; for example, this has a 40% chance