I often lose something. And as I'm looking for it, many times I find something completely different, "lost" time ago.
I had some old gear to repair and searched for 1mF/50V cap I surely had in that drawer... it wasn't here. But I found Russian clone of 74181 instead, so I decided to build 4-bit ALU and subsequently whole 4-bit computer (made of 74xx ICs) around it.