The buckle's moveable bar is made in Amsterdam by ADR
in a rectangle frame. The maker's mark of Andries de Roever, registered in Amsterdam 1792-1833, died 1845 in the city of Deventer. He was the owner of a big silver factory. He also held shop at the factory premises. To pass his master silversmith examination he made a pair of buckles. Your moveable bar shows the town mark of Amsterdam, kleine keur
or 2nd standard or 833/000 fineness, year letter O for 1797.
The frame itself is made in Utrecht, combined town mark year letter X(?) for 1805, kleine keur
or 2nd standard or 833/000 fineness
Below the combined town mark and year letter Y for 1806;
The silver guild town mark of the city of Utrecht is based on the city coat of arms: a crowned cross-divided coat of arms meets with vertical stripes in the vertical section. For more information see Utrecht:viewtopic.php?f=5&t=32028#p82869
The maker's mark BM
for: Benjamin Muyzert, registered in Utrecht 1798-1811.
The buckle is a marriage and/or repair.