Hi,
Indeed Dutch silver purse frame (gilded or gold?), maker's mark in the French style being a lozenge with
NT under a
spade for; Nathanael Teuter, active silversmith in Amsterdam, registered during 1796-1831, died in 1831. This particular mark used 1812/1825. Known marks used by Nathanael Teuter; N.T in a rectangle used during Kingdom Holland 1807 — 1811 ( French occupation), NT under spade in a lozenge 1812/1814 until 1825, NT under a clover 1825-died.
The year letter script
J. for 1818.
Please show us a clear image of circular mark; Minerva head(silver) or lion head erased(gold) and/or check for other marks like lion passant/rampant facing left for gold and facing right for silver with different frame/shield shape.
For more information French occupation or Napoleonic era see;
viewtopic.php?f=5&t=32028#p80300
Peter.