Sounds like it is for anti=tamper seals, probably a disk of lead to squeeze around a loop of wire holding whatever shut (here eg eletric meters, although they've used tubular lead or zinc crimps at least in my area for a long time, rather than disks). Photo of some lead disk anti-tamper seals stolen from an ebay auction:
Not sure if it's used for this, but UK power supply puts a ~100amp fuse before the meter. Once the cartridge is in place the holder cover is locked with a wire, then an alloy seal is pressed on the wire ends so tampering will be evident