I've certainly made my fair share of mistakes over the years. The worst was my super 20 silversonic alto a few years ago with a nude engraved on it. I got it perfect then started working on her face. Somehow she turned out UGLY AS SIN!!! She looked like a tranny, and not a Conn tranny either! I had to have her hair cover her face so no one could see the ghastly thing that dwelled beneath... luckily it turned out okay, but yikes! Engraving is incredibly difficult.
I remember when Bram flew me over to Holland to work on his collection and show him how to engrave. He handed me a mint condition 5 digit Mark VI, and what was the first thing my jet-lagged, exhausted self did with him staring over my shoulder? Slip. A nice big, fat scratch right across the bell. Our first lesson was how to cover up mistakes. I think he turned white as a sheet.
My first paid engraving job was mojo's Conn tenor, which was black painted with auto paint. I started engraving, and the paint started flaking off in chunks around the pattern! Yikes! I had to buy matching paint, fill in over the engraving, and then re-engrave it making sure the cut was consistent.
Oh! There was also the dreaded Oleg incident... he sent me a gold plated neck to engrave. I started to work on it, and my tool just slipped off and left a huge and nasty scratch. I figured I had just done something wrong and started to correct my mistake, again, it slipped off leaving ANOTHER nasty scratch. I called him up and asked what the deal was and he informed me the gold plating was over NICKEL! Now, nickel is nearly impossible to cut, and then with plating over it, there was no hope. So, I had to straight cut all the work on the neck, which can be done over nickel. It was the worst job I ever had to deal with.
Ahhh... luckily I never misspelled anything. Although I did kinda mess up the lettering on Ted Nash's tenor because the bell-bow band brass was uneven in consistency.