In recent years, there seem two have been at least two different designs for the flag of the Dominican Port Authority, though both follow the same pattern of displaying the Authority's seal on a blue field.
The Dominican Port Authority (Autoridad Portuaria Dominicana) is an independent agency of the Dominican Republic government charged with responsibility for overseeing and administering the National Port System, complying with national and international standards, while managing and directing the country's seaports and increasing international trade. [1] The APD was created on 17 December 1970 by Public Law 70-70. [2] Randy Young, 2 April 2020 Sources:
[1] https://www.portuaria.gob.do/quienes-somos
[2] https://www.portuaria.gob.do/historia
A image in this pattern was published in Flag Report in 1 April 2012, but info was elaborated at less one year before. The photo source probably was taken in 2010 or before. I believe that the flag was in use after many years, even from the XX Century. Jaume Ollé, 3 April 2020
image by Randy Young, 2 April 2020, based on original artwork by Wikimedia user Cheposo, 17 September 2013
There is a third design, still similar to the two already mentioned, that is shown on Wikipedia. This graphic was created in September 2013 by Wikimedia user Cheposo as his/her own work. While I can find no photographic evidence online to support that this design actually found use, it does fit the general pattern and would logically be an earlier version of the two already presented. The Wikimedia version shows the same Port Authority seal, but with the the ship's wheel, spokes, and braid all in gold. Randy Young, 2 April 2020 Sources:
[1] https://commons.wikimedia.org/wiki/File:Bandera_Autoridad_Portuaria_Dominicana.svg