I saw your posts on znachki and it prompts me to send you the link to my Instagram account, where I'm posting one a day from my collection.
https://www.instagram.com/sovietpinsrus/?hl=en

As a long time student of siege and obsidional issues, I have seen and handled many of these. The denomination for the one in the article is a Half Gulden. This is the most commonly seen type. There also exists a one gulden (a type that I last handled about 4 years ago). If memory serves me it was about a third larger than the ½ Gulden.

There also exists at least two and maybe more larger ones, the last one I saw and handled, about 40 years ago. I had two, and I think they were as large as a silver dollar or Thaler sized coin.

These were struck on Bible pages as this was the only thing available for these small denomination coins. There were other coins struck for the siege in silver, but this discussion is about the paper issues only. It is my understanding that Bibles of this period were made by a process known as illumination in which the type was large, some letters were not in black and the pages themselves were quite thick, the thickness of the coins struck. All were counter stamped with a lion, the mark of the province of Holland.

In my humble opinion, although of paper, these issues were made to circulate as coins. The people of Leyden (about 25 miles from Amsterdam, although I have not been there) needed coinage for everyday commerce while under siege from the Spanish. Certainly a very interesting item.

I will always be just a student as NO ONE knows it all. And I have always found square coins (and coins made out of paper) to be neat. Hence , when the internet started, my domain, is Klippes.com

I did some internet searchng on American research in Leiden coins 1574. Very interesting, a lot of attention !

I came across another error ; the countermark applied was not "By order of Prince William of Orange ... " etc. That was the countermark of 1571/72 (tax to finance the war), but they used the same die to countermark the paper coins in Leiden 1574 ; the small die with the lion in a circle of pearls. The reason is very obvious : this countermark was still kept and available at the City Hall !!

This countermark was not for tax but only to show the users of the paper coins that they were genuine and no falsifications which were discovered shortly after distribution. It is also not true that the countermark was applied after the siege to make the coins invalid.

I am the niece of the late Robert Martin. As time goes by, more & more information about Robert's collection is becoming familiar to the family. Uncle Bob would always visit us in Orange County NY where his brother John (whom just recently passed away) lived and would continuously try to educate the family on his coins / collections. Uncle Bob would always have a few coins with him for show & tell. I knew it was a passion for Uncle Bob but only since his passing did we realize how valuable it could be due to its rarity.

A magazine came to the house addressed to Robert last week titled "COINage". This morning I took the time to educate myself for the reason of the cover "Ultimate Secrets of the Coin Auctions" and found on page 22 a photo of the late Walter Breen who is in a section of one of your articles with a photo named "Midnight Sale" along with Uncle Bob. I did read this article shared with the family back in December 2017 and again today after reading through the magazine noted above. I was taken aback by the testimonials that Randy Clark, Mike Packard, Anthony & Mary Ann Terranova, Roger Siboni and Jack Howes wrote. Today it hit me that Bobby was very well liked by many and a huge educator in the coin world.

This hobby of Uncle Bobby's is completely like a puzzle being put together. I just wanted to share with you that we as a family appreciate the knowledge shared of Uncle Bob's coin life and a special Thank You to those noted above for sharing their memories

The Heller article you referenced uses the phrase "specifically named people". Under that criteria, the three remaining folks are probably (Englishman) General John Burgoyne (1863 $500 National Bank Note), (Spaniard) Hernando DeSoto (1918 $500 Federal Reserve Note) and (Englishman) Sir Walter Raleigh (1875 $2 National Bank Note).

There are numerous other non-Americans depicted on US currency, including King James I and Queen Anne, Brigadier General William Phillips and Lt. Gen. Baron Friedrich Adolph Riedesel, but they are not "specifically named" on the notes themselves, but rather identified from the original source of the vignettes in which they appear.