Hello Beau,
The maker’s mark is IK for Jan Kleyn, Schoonhoven 1767-1806. The year letter K, I believe is for 1803.
The maker's mark of Jan Kleyn, Schoonhoven 1767-1806, with known variations:

The year-letter K variations seen:
Jan Kleyn a known button maker. His buttons are found worldwide and those days worn by 'everyday better of man and woman', see:
viewtopic.php?f=5&t=40198&p=112153&hilit=jan+kleyn#p112153Best,
Peter