Everything is real fuzzy on this subject.
Some reported "Facts"...
92.5 was used in Europe as far back as the 14th century.
1868 in the US is when it started to be used but not a whole lot.
1906 is when the mark supposedly became a requirement in this country but not many cared because Ster or Sterling was still being used up until the late 60's at least...into the 70's probably and even up till today.
In 1973 Europe had the Vienna Convention establishing the 925 Common Control Mark among several European nations .... 925 became a sort of "international indicator" from that point forward....but not always.
Don't know if there is a definitive answer, the 925 mark and all the others have been in use for way more than 100 years, centuries, actually, but that does not mean everyone used it or even uses it today.
If there are laws governing this not everyone out there seems to care to be following them, artist types sometimes follow their own paths...some larger companies, too.
Most everyone knows what sterling means but a whole lot have no idea what 925 represents so companies might keep this in mind when marking, and marketing, their jewelry.
I can tell you I have found a ton of silver jewelry marked 925 but I have also found a whole lot marked only sterling and a few marked simply Ster.
I can guarantee you a few of those marked with either word are not really that old at all, one religious medallion I found only marked Ster was not worn at all, looked almost brand new and was not very deep in a public park.
Found around 2015 and I doubt it was more than 10 years old, if that, so I think 925 is more common but Ster and Sterling still seems to be in use.
A conundrum, but like my wife this might not ever be figured out definitively or satisfactorily.
Now go have one more big drink and then think seriously about cutting back a bit.
Maybe try yoga or meditation, could help calm the nerves but definitely not as much fun at parties.