File:Tinkering-trivial skillup2.jpg

Summary
Here is another example of gaining a Tinkering Skillup from a trivial item. Notice in the screenshot that the item crafted is Spring-Loaded Gnomish Stilts, which is a 60 skill item (level 12), but the skill gain is 376/380 (level 76).

So it appears that it is possible to gain tinkering skillups from virtually any level of Tinkering item.

This screenshot was taken on 3/6/2008.