Danish West Indies
The emphasis on transit mail between the islands of St.Thomas and St.Croix has mostly centered on the St.Thomas to Christiansted route via the schooner "Vigilant" - but many other ships were used for carrying mail. There was an active direct ship route between St.Thomas and Frederiksted. These letters will only show St.Thomas and Frederiksted postmark and the cancels may be two days in between.
Printing 4 - St.Thomas (Tuesday) 27 January with Frederiksted (Thursday) 29 January arrival cancel.
The envelope was cut open and has a filling hole in the bottom left corner. Some businesses would punch a hole through the envelope and content and hang it on a hook until the correspondence was answered. This may be commercial mail rather than philatelic.