Friend Phez, I am a machinist. It's what I do. Every day for 12+ years. It's what I went to school for. And I am good.
I tell you this so that you understand where I'm coming from. And that my answer isn't some ill-informed claptrap.
If someone handed me this, and said "I need this sort of nowish."...
...I wouldn't go shopping for a specialized button tool, or grind a custom tool like I would for making multiple production pieces. I would just use the turning tool that LIVES in my lathe's tool block...
...because it is more than capable of cutting those grooves, and unlike a button tool, it will bevel the backside of the groove on it's own. The only downfall would be that I'd need to try to match the bevel on the front side by hand. I'd hit it with a file, or even the same tool while breaking the corners of the ridges I just created.
Cutting those grooves by this method would take about 5 minutes per part. Less time than it would take to procure a specialized tool, even if I already owned it, as the lathe is ALWAYS set up for this process. The ridges would just be a bit...asymmetrical. Not so much as to be obvious to the average person, but under the scrutiny of a trained eye...
I'm not saying that that's what was done. But I am saying that were I the BBC prop guy, that's how I'd have done it, and that's how it looks to have been done to my eye.













