Now it can be told. The tool is for making holes in network cables so you can attach a Vampire tap to them. In the olden days Ethernet networks were made of a single thick piece of co-axial cable (the same stuff we use to connect TVs to aerials). This had a terminator at both ends and the way you connected a station to the network was to drill a hole in the side of the cable and push a pin into the central conductor. These connectors got the name of “vampire taps” for obvious reasons.
Getting the hole wrong (too big or too deep) was bad, as you only had the one cable for your entire network. So we used to use a device with a drill bit which had been cut to just the right diameter and depth in the tool you see above.
This was in the “Good Old Days” of networking, 10BASE5 style (this means 10MBits/second, baseband signals and 500 metre maximum segment length). Nowadays we are up to 100GBits/second on some networks. That is 10,000 times faster.
The tool has rattled around in my desk for a while and I probably should get rid of it.
Having said all that, it does remind me of a Veroboard track cutter. I used to have one of those too. It’s a tool which lets you make breaks in copper tracks on circuit boards by cutting through them with a drill bit. So, I reckon that Dave G is a winner here and if he wants to drop by he can have is Windows Phone lanyard.