I've made ten lead lunchboxes instead of tin ones. Is this intended -- perhaps as part of the "any metal" feature? Or is it a bug? The only way I can figure it happened is that I activated the lead sheet when combining it with the tin sheet at the start. Since I had to add more tin sheets after, it isn't following the "last-main-material-type-added" paradigm.
Edit: I've now tested with both the tin sheet and the lead sheet activated at creation; the result in both cases is an unfinished lead lunchbox. I also tried to use an iron sheet to combine with either a tin sheet or a lead sheet (to test whether this was a function of "any metal"); neither combination yields the menu option to create a lunchbox.