I might as well add the information that I've found:
From Cash 1991 (before rediscovery):
"Distribution: North Vietnam is the documented source of this species, although locations in the central portion of Vietnam have been reported as well as Yunnan Province, China"
From Cribb 1987 :
"... this species was introduced from an unspecified locality in North Vietnam (Tonkin) where it was discovered by a French army officer in 1913 or 1914. ... Poilane rediscovered it in 1922 near Nha Trang in Vietnam.
... All of the plants in cultivation are thought to derive from one of these few early introductions of plants into France. ...
Recent rumors suggest that it might also be found in south-west China."
From Averyanov et al. 2003:
"The discovery of Paphiopedilum delenatii was attributed to a French army officer who bought [sic] to France in 1913 or 1914 pink flowered Paphiopedilum specimens from an unknown locality of northern Vietnam. ... No undoubted herbarium documentation has yet been found for these plants. It is possible that this first report of a pink flowered-slipper orchid from northern Vietnam was based on Paphiopedilum vietnamense or P. micranthum, both discovered 85 years later. Anyway, the report of Paph delenatii by Guillaumin (1934) in northern Vietnam (Tonkin) is almost certainly mistaken.
Paphiopedilum delenatii was was certainly discovered by the French explorer Poilane in 1922 near Nha Trang city of southern Vietnam."
From Birk 2004 :
"Range: Tonkin(?) north Vietnam; recently in Nha Trang area, S. Vietnam"
None of that helps substantiate the presence of delenatii in China, and some calls into question it's presence in the north of Vietnam.
That said, it seems quite clear that the plants in cultivation prior to rediscovery in the early 1990s were of a slightly different character. This might be simply a result of human selection from a larger population. The newer plants seem to have darker pouches, while the blooms of many of the older ones seem to be mostly white with only a bit of a pink blush. I have also heard that the older ones tended to be more fragrant.... let me know if any of you can substantiate that.
Whether or not delenatii is found in China, though, it seems that calling the older strains Chinese is a mistake, as there is no evidence to suggest that they are Chinese in any of the accounts I've seen. I guess I'd better stop
As Ever,
Matthew Gore