Kudos to you -- especially amida17!
Yes, this is the reverse of the Hudson, New York Sesquicentennial commemorative half dollar.
But, here's another quandary.
The 2012
Red Book claims Neptune and his trident are on the reverse of the coin. Conversely, the US Mint's website from their historical area claims the seal of the City of Hudson, New York is the coin's obverse.
You get to decide which you think the image represents -- obverse or reverse.
As for the hints, they were obscure on purpose, but that didn't deter several of you from identifying the coin. Congratulations on your knowledge of classic commemoratives!
Even though Hudson, NY is several miles inland, the early Dutch settlers thrived from a seafaring economy, for example, whale oil. When kerosene began being used in lamps instead of the whale oil, the area saw a significant loss in their economy.
Fast forward a few years and the area preyed on people's vices. Fifty or so bars thrived in the city along with gambling and a large red light district. During his term, Governor of New York, Thomas E. Dewey, played an instrumental role in breaking the vice rings of the Hudson area.
The book, Diamond Street: The Story of the Little Town with the Big Red Light District by Bruce Edward Hall tells of the shadier side of Hudson.
Regarding the seal of Hudson, in the 1862 book by Stephen B. Miller (Historical Sketches of Hudson, Embracing the Settlement of the City, City Government, Business Enterprises, Churches, Press, Schools, Libraries, Etc.), the city's seal was purchased in 1785 -- the first year of the city -- by Nathaniel Greene, Seth Jenkins, John Bay, Ezra Reed, Stephen Paddock, Benjamin Folger, Dirck Delamater, John Ten Broeck and Peter Hogeboom. They each contributed eleven shillings and four pence. Mr. Miller stated, "This seal is still in use, never having been changed." But, that was 1862.
Now, a few Google searches haven't found an up-to-date image of the Seal of Hudson, New York. It would be interesting to know if the seal purchased in 1785, the image of the seal on the 1935 Hudson Sesquicentennial coin and the official seal today are similar or different.
The searches on city seals along with Neptune found mention of other parts of the globe, such as European cities, that have Neptune as part of their seals.
Another interesting search result showed details of a medal rather than a seal or a coin. The Medallic History of Oliver Cromwell describes a medal showcasing "Neptune on a car, drawn by two sea-horses: the shields of arms of England and Holland resting on his knees, between which is a wreath. He holds a trident in his right hand, and...."
But back to the coin challenge, congratulations to all of you who recognized the Hudson Sesquicentennial with a big WELL DONE to amida17!