Jacob van den Werf, notary, wrote Letter L-535, the notary act whereby Leeuwenhoek received a medal from the faculty at Louvain
In 1716, Leeuwenhoek received an honorary medal from the University of Louvain in what was then the Spanish Netherlands, now Belgium. They addressed it to "the highly honoured and widely famous Mr. Anthony Leeuwenhoek" for his "never yet properly appreciated and celebrated discoveries in Natural Philosophy". 
The letter and medal were delivered via Delft brewer Gerard van Loon, recipient of the letter, on May 16, 1716. The receipt was recorded in a document prepared by Jacob van der Werff, notary.
An associated book of praise poems was published the following year.
Lauwerkranssen, gevlochten voor den heer Antoni van Leeuwenhoek, groot wysgeer, lidt der Koningklyke Gemeenschap te Londen.
Laurel wreathes, plaited for Mr. Antoni van Leeuwenhoek, great sage, member of the Royal Society in London.
A week later on June 6, Leeuwenhoek replied:
Mr Gerard van Loon, barrister, has delivered to me an obliging letter of Your Honours, dated the 24th of May last, and a purse of gold cloth, within which a commemorative medal of silver rested in a little black case, one side of which showed my effigy and the other side an emblem, the town of Delft in the distance.
In 1731, van Loon featured this medal in his own Beschrijving der Nederlandsche Historiepenningen, source of the image on the right (click to enlarge).
ONA Delft inv. 2611, Jacob Van Der Werff, notary. Copied and pasted from Collected Letters, vol. 20, "this volume" in the footnotes.
On this day the 3rd of June 1716 appeared before me, Jacob van der Werff[1], notary at the court of Holland, admitted, residing within the town of Delft, in the presence of the witnesses hereinafter named, Mr. Gerard van Loon[2], brewer at the brewery called De Verkeerde Werelt within this town[3]; and declared that by him present was duly received a letter bearing the superscription: To the highly honoured and widely famous gentleman, Mr. Anthony Leeuwenhoek, etc. at Delft, under cover, together with a silver medal [Fig. 1], having graven upon the obverse thereof the portrait of the said Mr. Leeuwenhoek, encircled by the words Anthony Leeuwenhoek Reg : Societ : Angl : Membr. and upon the reverse thereof the town of Delft in the background, with the subscription In tenui labor, at tenuis non Gloria[4]. It was enclosed in a little horn box, lined inside with velvet, and in a little bag of woven gold, sent to the appearing party (as he explained) by Mr. Anthonij Cinck[5], professor of philosophy, canon of Liege, prebendary of St. Peter’s at Louvain, president of the College of Cranendonck, etc. etc., with written accompaniment and earnest request that the appearing party should be pleased to take upon himself the charge of delivering the foresaid letter, medal, box, and bag to the said Mr. Leeuwenhoek, on behalf of Mr. Cink and the other professors of medicine and philosophy at Louvain, as an honourable gift and recognition of their appreciation of his, Mr. Leeuwenhoek’s, never yet properly appreciated and celebrated discoveries in natural philosophy. This foresaid letter, medal, box, and bag, according to the charge aforementioned, on receipt thereof from the appearing party, has been handed over to Mr. Leeuwenhoek.
Appeared likewise before us, notary and witnesses, the oft-mentioned Mr. Anthonij Leeuwenhoek, living within Delft, who declared that he had received the foresaid letter, medal, box, and bag from the hands of Mr. Van Loon, declaring that he gratefully accepts the gift of the earlier-mentioned professors, as he confirms by this [declaration], thanking further Mr. Gerard van Loon for his efforts and good care of this official gift, and by this [declaration], completely discharging him. So all parties declared to have knowledge about this [gift], which has been formally declared in this document.
Done within the city of Delff, in the presence of Frederik Matie and Rutgerus van Brienen, both requested as witnesses of this occasion[6].
Gerard van Loon
Antonij van Leeuwenhoek
Frederick Maatje
R:V: Brienen
Jacob Van der Werff, nots.
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[1] Jacob van der Werff (1682-1736) was admitted as a civil-law notary in Delft on 7 December 1708. He lived on the Oude Delft near the Boterbrug. He married Sibilla Hoppesteijn van Leeuwen in 1731 and was buried without offspring in Delft on 10 January 1736.
[2] See Letter L-535 [XXV], in this volume.
[3] The Delft brewery De Verkeerde Werelt (The Faulty World) was operated by Gerard van Loon, together with his mother, Judith Kruijck († 1727), widow of the Delft brewer Antonij van Loon († 1709) and his brother, the painting collector Jan van Loon (1633-1685). In 1736, their brewery went down in a high-profile bankruptcy. See: Zuidervaart, “Een nieuwe theorie”, p. 21.
[4] Motto derived from Virgil, book IV, line 6: “Slight is the subject, but the honour is not small” (referring to bees). See for this homage, comparable to a present-day honorary degree, Van Loon, Beschrijving, vol. 4, p. 223. For the medal and its imitations, see Groenendijk, ‘The 1716 Van Leeuwenhoek Medal’.
[5] See Letter L-535 [XXV], in this volume.
[6] The two witnesses – Frederik Maatje and Rutgerus van Brienen – were still very young in 1716. They both were confirmed in the Dutch Reformed Church of Delft just the year before, in March and September 1715, respectively. At that time, Maatje (also known as Matie) lived on the Buitenwatersloot, and Van Brienen on the Voldersgracht. By November 1725, Van Brienen had moved to the Vlamingstraat. He was at that time a butcher, with a stall at the meat market.
