Hi Maurice,
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Assuming we are looking at a Dutch city guild mark and being pushed to give an answer; Hoorn mid-18th century. If turned 180 degrees, the shape of the shield; similarity to Dokkum early 18th century.
The problem with silver buttons or small silver items below 20 grams in general; often the local hallmark rules of the guild did not apply or were not upheld. Often you find only a letter or other obscure mark, sometimes struck twice and struck by the silver smith, no assay office involved and if you are lucky you have maker’s mark with an assay city mark or even better including a date letter.
I do not know if you can recognize, by the shape or design of a button, in which country or province city the button has been made. But sometimes you can, like the traditional silver used in fishing/farmer communities (folklore). Foreign travelling merchants were unofficial allowed to sell small silver items directly to the villagers and farmers but only silver items below a certain weight, those items could be without marks or maker’s mark struck only and in low quantities otherwise the local silversmiths would complain to the guild authorities.
Oel.