To close the loop: Contrary to what Prynt support told me  in November about Prynt Zink 2x3 inches - Is printable area 620x1120 or something smaller? the Prynt printable area is 2 inches by 3 inches (at least it is with the Samsung S5 Android Prynt App as of June 23, 2017)
 Prynt support email response from November 22, 2016
Thanks so much for reaching out! Great question! The actual printed area is 620x1120 px.
Please let us know if you have any other questions- we'd be happy to help!
On Mon, Nov 21 at 6:41 PM , Roland Tanglao
"The Prynt Case uses ZINK® (Zero Ink®) Printing Technology that produces photo-quality, full-color photos (313×339 DPI or 620×1120 px)" Can i print on the full 620x1120px or is the actual area that is printed smaller? If smaller what are the dimensions in pixels? Cheers! ...Roland