Thanks Gerd! Great puzzle.
One suggestion for the next one. Would it be possible to identify one category, such as Rust in this puzzle, differently than the other category, such as Hint in this puzzle? I found using numbers for both categories quite confusing. I realize using letters for one category can be difficult, especially when there are more than 26 items, but I certainly find totally separate identification systems much less confusing in the heat of the chase.
Again, thanks for a great puzzle!