Is this a plaque or a medal ? Also, what is it ?

It is pretty big for a medal, but it is two-sided, with space for engraving and a loop for suspension. The $2 bill is for size comparison.
As far as I can tell without further research, the "Digressionists" was a small art movement in the early 1900s related to alternative art forms and architecture. It was possibly connected to the "Century Association" and/or "Century Club".
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Comments
Nice medal.... Reminds me of my Navy days... always saw a lot of flying fish. Then, when I lived in Barbados, I found out they are really good to eat.... very tasty. Cheers, RickO
A real nice medal.
Holy Mackerel that is cool!
In honor of the memory of Cpl. Michael E. Thompson
Wrong forum. /s
https://forums.collectors.com/categories/u-s-world-currency-forum
peacockcoins
"In 1906, Charles Ewing formed the Digressionist Society with fellow New York architects,
James Monroe Hewlett, and Grosvenor Atterbury. The Digressionist Society consisted of a
group of well-known architects and artists whose mission was to create something artistic
outside of their usual purview, to be unveiled and evaluated at their annual convocation. The
winner, chosen by three judges, was presented with a medallion engraved with the
Digressionists’ symbol, a flying fish, and an image of the Acropolis beneath curling waves. (FN
James Monroe Hewitt Article). Charles Ewing is reported to have received the "Flying Fish"
award several times, although it is unknown at this time for what."
From United States Department of Interior's National Register of Historic Places Registration Form for Timber Point in Biddleford, Maine.
https://www.fws.gov/uploadedFiles/TimberPointNationalRegisterForm 2012_10-900_final.pdf
Excellent information, thanks.
As I suspected, the flying fish is symbolic of going outside one's traditional environment.
Also symbolic is the classical architecture (Acropolis) left behind under water.
PS:
I saw it on eBay, for a little over $20 shipped, so I decided to add it to my plaque collection.
The seller had no specific information about it:
https://ebay.com/itm/324739794800
Very cool! I like the symbolism, and the price was very reasonable. Nice find!