Chubb padlock

Hello All,
Would anyone be able to narrow down the age of manufacture for this Chubb Padlock.
Serial 168645
And is marked “Makers to His majesty”

I have another similar padlock that is marked “Makers to Her majesty” that dates 1895.
Im guessing this one is older?
Thank you,
Dean

I would have expected a 7-digit serial number, and that would make it around 1913.

Thanks Magpie,
I have found a Chubb production list but I’m not sure if I’m on the right track.

1838 - 1882 Horseley Fields, Wolverhampton #19801 - 899500