Interesting! Thanks, Greg. I couldn't read the top line and a Paquebot cancel never occurred to me. My copy of Gibbons says that a British Packet Agency was established on Guadeloupe in 1848 and continued to operate till 1874. I make the date on my OP as 1873, so your idea looked good. I searched on line and found this link, showing the exact cancel on my stamp. You nailed it!
https://www.franceandcolonies.org/d...d%20Blue.pdf