There’s only 10 dates / years of issue for the Netherlands 10G coin during the 41-year reign of Willem III. All of these years occurred in a 15-year period from 1875 to 1889. Because of this, he only had one official portrait during this time and all the coins have the same obverse. Because even the date is on the reverse there is absolutely no way to discriminate one issue in the series from any of the others by just looking at the design of the obverse. By contrast, his daughter, ruled for 58 years (longer, but he was still on the throne 4 decades), and Gherrmann44’s 10G set honoring her has, I think, four official portraits on the obverse.
The reverse of the coin is a different story. The 10 issues use a total of three different reverse “designs” for lack of a better word - or so I thought. It’s really two different designs and one of those designs has two variants with different privies… but I’m getting ahead of myself.
The 1875 - the first and by far the most common with a mintage (4,110,00) that exceeds that of all the rest of the series combined (3,719,657) - is a 1-year type coin (KM 105).
In 1876 several design features were re-arranged, and the date moved from the top to the bottom of the design. All the coins made from 1876 to 1889 are the same type (KM 106) and are the same except for one small detail: one of the two small marks on either side of the year is different in the last issues of the series. The issues from 1876 to 1887 have a battleax to the left of the date. The 1888 and the 1889 have a halberd.
I have wondered, literally for years, what these marks were and why that one changed at this point. It never occurred to me that these were the mint mark and privy mark. I’m not gonna lie; this makes me feel a bit dumb.
How did I figure this out? By reading the coin descriptions on Coin928’s “Curacao 1900-1948, Complete Circulations Issues” set. On more than one coin in that set he explains that the fish on those coins, next to the date, in the same position as the battleax and halberd are on the 10Gs, is a privy mark. The symbol on other side of the date is the mintmark for the Royal Dutch Mint - it’s a “Staff of Mercury.”
He was nice enough to give me a link to the site where he found this information.
The battleax is the privy for Philip Hendrik Taddel, who served as Mint Master from Nov 1874 to May 1887.
The halberd (hellebaard) was the symbol for Hugo Laurens Adriaan van den Wall Bake (Good grief! What a name!), who served from July 1887 to 1909.
Thanks to Coin928 for the new resource (website) and the information.