Overstamp

[Stamp 0]

Hi, I wonder if anyone has come across or can identify this overstamp.

it is on a 1701 William 111 silver coin.

Thanks ,Stamp.

[Peckris 579]

A complete shot in the dark: G M could stand for Gulielmus Maria, the Latin names for William and Mary as on their coin legends. The difficulty is that Mary had been dead 7 years by 1701. 

[Stamp 0]

Hi peckris, thanks for your answer. 

So, stamped by the mint ? But would it not be more common.

[Peckris 579]

2 minutes ago, Stamp said:

Hi peckris, thanks for your answer. 

So, stamped by the mint ? But would it not be more common.

No, not a mint stamp. Maybe some Customs and Excise thing, or a company's initials? I don't really know. Never seen it before.