Prussian, Customs Seal, Frederick Wilhelm

Prussian Seal, Frederick Wilhelm, Image & Found by Folkert.
Found in Germany, 20mm.

"The reverse doesn't show a bee, but the prussian eagle, the ligature reads FWR = Fridericus Wilhelmus Rex (= King Frederick Wiliam). But I do not have any idea about its age: it could be any of the four prussian Kings with the name Friedrich Wilhelm:
Friedrich Wilhelm I. (1713–1740);Friedrich Wilhelm II. (1786–1797); Friedrich Wilhelm III.(1797–1840); Friedrich Wilhelm IV.(1840–1861).
Judging from the style, I think the seal could be attributed to the reign of Friedrich Wilhelm I." (Information supplied by Folkert).