Dutch silver - Script I Mark

[cherivh]

On the page of this site dedicated to hallmarks of the Netherlands it shows a script I (image J under "Examples of Dutch Hallmarks") which is described as
"a tax mark for old Dutch made silver items that came back into
circulation which did not bear an older tax mark, it can be found as the
only mark on some pieces and does not guarantee any particular standard
in these cases."

When was this mark first used? How old would a piece have had to be at that time to be considered an "old Dutch made silver item?"

I recently acquired a lovely agate brooch in a Medieval Arts & Crafts style bearing this mark and am trying to pin down the date as best as I can.

Thanks!

Cheri