It looks you have an Electro Plated Nickel Silver.
The technology is not old enough to origin from 18th century.
From a site where you can find identical font type:
Modern electroplating was invented by Italian chemist Luigi V. Brugnatelli in 1805.
And the picture which is similar enough:
So the number as Steve Bird suspected correcty it should be a batch number. Most probably your item and this one made in very different series, but the material is the same. It doesn't contain silver, it's content typically are: 60% copper, 20% nickel and 20% zinc. This formula also known as (in)famous german silver, beginner silver investors sometimes fall into the trap mixing up it with real silver. It's density is significantly less than real silver. It is 8.3 gr/cm3 instead of 10.5 gr/cm3.