[Tractorfan]

Hi,
Later MK plugs had a black plastic disc that covered the rivet for the fuse holder. This was often lost leaving the rivet exposed. I suppose the main risk was a flashover if the plug was used with a metalclad socket in humid conditions, but I've never heard of that. When the plugs with the larger finger shields were introduced, the disc was made from the same fibre material as the cord grip. Again, these would sometimes fall out.
The other photos show an Ashley plug with a fibre plate to obscure the entry hole when used with thin flex. These are often lost as well, so I suppose this brown example is a bit of a rarity.
I also have an MK leaflet which shows the standard plugs plus the "New SafetyPlug". It is shown with a fibre band & screw type cord grip instead of the later springy plastic "tongues" type of cord grip. I have never seen an early type, so wonder if it was ever sold?
Cheers, Pete