Well, it appears there is an answer to this mystery. I sent a request to Chris Wright (Warship International editor) and Charles Haberlein (until recently retired, the NHHC Photo Collections director) and they narrowed down the candidates and found a likely ID.
From Charles Haberlein:
I'm far from an expert on things French (which this one certainly is), but my suspicion is that it's a Chamois class minesweeping sloop (Aviso de Deuxieme Classe to its proud owners). My trusty 1950 "Flottes de Combat" lists seven of the suckers (with pendant numbers): Chevreuil (A 10), Gaxelle (A 08), Annamite (A 09), Bisson (A 05), Commandant Ducuing (no number given), Commandant Amyot d'Inville (A 07) and Commandant De Pimodan (A 06). The first three listed were completed before the Germans made France their own, and the last four entered service after the nice Germans went back to the Fatherland. "Flottes de Combat"'s drawing & photo of Bisson does not look like the ship in the photo, but its sketch of Commandant de Pimodan resembles it reasonably well and
its photo of Commandant Amyot d'Inville is nearly a spitting image. But for the fact that I don't know the subject very well, and don't have access to photos of all of the class, I'd be inclined to put my money on the latter.
From Chris Wright:
Kudos to Mr. Haberlein. It happens that our eminent French friends have published a superb and definitive volume on "Les Avisos-Drageurs Coloniaux de 647tW du Type Chamois", written by Charles Salou and published this year by Editions Lela presse. It describes these vessels in copious detail (available to all at 42 Euros per copy.)
The vessel in question almost certainly is Commandant Amyot d'Inville, wearing pendant A53 in the photos in this French book. That number looks like it could match what you have. The only other possibility is Commandant de Pimodon, but the photos in the book lack any pendant number on the hull where it appears in your photo. Plus the Pimodon 1947 photo lacks the 20-mm guns on the forward deckhouse, though they were added by the early 50s (and by which time the bridgeword was modified noticeably.) The forward deckhouse and bridge of the two vessels, both built by the same yard, look essentially identical as completed. Both received the same hull paint scheme upon completion. And the two headed out together at the end of 1947 to Vietnam, returning to metropolitan France in 1950 (Pimodon) and 1955 (Amyot d'Inville).
Looking up via Google for Commandant Amyot d'Inville, I found this website ...
http://www.netmarine.net/bat/avisos/amy ... ancien.htm ...
(English translation ...
http://translate.google.com/translate?h ... 6prmd%3Div ...)