It’s likely to be a sign of our age when we can recall BBC announcers ‘on the wireless’, asking us to call Whitehall 1212 (Scotland Yard) if we wanted to report anything suspicious. I was too young at the start of WWII to understand the significance when I first heard it. I did know Billy, my friend down the road, had a secret he wouldn’t tell his mother about.
Regarding 6255456376, MichaelG, barking up the right tree as is so often the case, got it in one while allowing me a bit of chuckle time.
Other answers were coming close with ESSO.OIL and SHELL.OIL from older style upside-down calculators.
However, insomniacs and night-time clock-watchers might realise that the numbers represent the number of segments displayed for 0 to 9 in the seven bit numerals of a digital clock etc.

If sleeping doesn’t come easily, and the digital clock is in full view, what about those other number patterns? For example, 232, or 555, or 437, or 327, or 127, or … has anyone still got their 1250 or done a 252?
Well, counting sheep is so old fashioned.
Keep safe,
Sam