It’s fascinating what hangs around in code-bases for decades. Following a recent update, Microsoft Excel files in a certain format (the old style .xls files rather than the .xlsx files) started showing up with this icon:

Which I haven’t seen for a couple of decades. More interestingly, the smaller version of the icon was this one:

What has this to do with Excel? It looked vaguely familiar, but I couldn’t place it. After a bit of thought and Googling around, I realised that this was the icon for a program called ResEdit, which was an editor for binary files that I remember using back in the pre-OS X days. Looking at this further, I realised that the last version of ResEdit was made in 1994.

How did these suddenly appear? There are occasional references to this happening on various Mac forums from the last few years. I suspect that somehow they are in collections of visual assets in codebases that have been under continuous development for the last 30 years or more, and that somehow some connection to the contemporary icon has been deleted or mis-asssigned. I’m particularly surprised that Excel wasn’t completely written from scratch for OS X.