The above is a copyrighted picture reproduced here by permission. © 2007 by Jochen Wilke.
Quarterly; [1 & 4] Or, a lion Sable.
[2 & 3] Gules, a log in bend sinister with 3 stumps raguly (Argent ?).
For the above picture, Jochen Wilke used a design consistent with the flamboyant baroque style typical of Leibniz's own times. The seven-pearl coronet is a German baronial crown (Leibniz became a baron in 1711). Pending further investigations, the tincture of the charge in the second and third quarters is assumed to be Argent (it could turn out to be "Or" or "Proper").
Wilke quotes a private communication from Prof. Dr. Herbert Breger (of the Leibniz-Archiv in Hanover) indicating that the arms were originally granted to Paul von Leibniz, who was knighted by the Emperor on August 3, 1600. Paul von Leibniz was a nephew of the great-great-grandfather of Gottfried Wilhelm von Leibniz. Paul died without heirs and his arms were eventually adopted by other family members, including Gottfried Wilhelm and his half-brother (according to the work of Totok & Haase: Leibniz. Sein Leben, sein Wiken, seine Welt, Hanover 1966, pp. 8-9).
In a 2006-06-14 forum discussion, Friedhard Pfeiffer quotes the following German blazon from Die Wappen der deutschen freiherrlichen und adeligen Familien in genauer vollständiger Beschreibung, mit geschichtlichen und urkundlichen Nachweisen by Prof. Dr. Ernst Heinrich Kneschke (Leipzig 1855-1857) itself listed in Bibliographie zum deutschen Adel 1200-1999. It's not clear whether the parenthetical guess about the tinctures is from Pfeiffer or appears in Kneschke's original text...
Geviert, 1 & 4 ein rechts gekehrter Löwe,
2 & 3 ein Schräglinks gelegter, oben und unten abgehauener,
an der rechten Seite zweimal, an der linken einmal geasteter Baumstamm
(Farben vielleicht: Gold-blau geviert, roter Löwe, silberner Baumstamm).
Bahlsen advertisement for Leibniz-Keks (c. 1900)
Leibniz-Keks is a very popular brand of plain butter cookie. This German Butterkeks is a carbon copy of the French petit-beurre (invented by Lefèvre-Utile in 1886) down to the pattern of its serrated edges (with 52 teeth). Leibniz-Keks have been produced by the Hanover-based Bahlsen food company since 1891 (the Choco Leibniz is another related cult cookie). The name of the cookie is now so ingrained into German culture that native German speakers could only interpret the humorous term Keks-Wappen (coined by Jochen Wilke) as denoting the arms of Leibniz. Similarly, we're told that the Leibniz Gymnasium of Remscheid (Nordrhein-Westfalen) is colloquially known as Keks-Penne.
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