Hi, FRP the maker's mark of Frederik Rudolf Precht I , registered in Amsterdam 1744-1787, has also been encountered as a falsification as mentioned by Citroen and shown in the book "Valse zilvermerken in Nederland ".
Normal would be one maker's mark one proper town mark for Amsterdam in combination with a year letter.
The maker's mark AJ*Dr is for: A.J. Driesen, registered in Utrecht/Bunnik/Venraij 1957-1983
For some more information about the Driesen dynasty of silver smiths see: viewtopic.php?f=5&t=26413&p=116936&hilit=Driesen#p116936