The organ was built by an unknown organ builder, likely "Master Harmannus from Groningen" according to the Wikipedia article, in the years 1457/1513. The instrument was initially set up on a rood screen but moved to the loft at an unknown time, possibly in 1513 (the "organists' pulpit" was attached to the loft in this year).

Several repairs and alterations have been carried out over the centuries. These include repairs by Joachim Kayser in 1680, Valentin Ulrich Grotian during 1689-1699, and transformations into an instrument with a slider chest no later than the late 17th century, possibly as early as 1513.

Between 1736 and 1738, the organ was remodeled by Matthias Amoor, using parts of the wing doors for other purposes. Because of this, Baroque carvings by Jacob Tÿlman were used as replacements. Further repairs were done periodically throughout the 18th and 19th centuries.

In 1867-1868, the casing was shortened due to the addition of a new ceiling. Between 1880 and 1890, the keyboard and the stop knobs were renewed, most likely by Johann Diepenbrock.

The organ underwent an improper restoration in 1941 by Karl Puchar, which involved the replacement of three registers that were largely in their original state up until then. A comprehensive restoration was administered by Ahrend & Brunzema workshop under the advice of Cornelius H. Edskes between 1959-1960. This restoration aimed to revert the organ back to its mostly original state and to reconstruct the three missing registers.

Another restoration occurred from 1996 to 2009 during a church restoration which meant cleaning by Hendrik Ahrend. This stage also included the gilding of the facade pipes. For more detailed information on alterations, one can refer to the extensive Wikipedia article about the organ.

Additionals:

https://organindex.de/index.php?title=Krummh%C3%B6rn/Rysum,_Kirche