When: Here's the back -
The stamp-box, AZO with two triangles up and two triangles down, dates the picture to between 1910 and 1930 .
Next the Hong Kong Girl Guides website helps us narrow the range. It says that "The first Company in Hong Kong was formed in the Victoria British School [in 1916]" . But the girls in the photo are Brownies (younger than Guides), so when did they first appear? The earliest result from a search for brownie in the HKGRO and local newspapers is 1922.
It looks as though Brownie Packs got going in Hong Kong the 1920s. With a range of 1920-1930 to choose from, I'll guess the middle, c.1925.
What: Do we have any ex-Brownies reading, who can explain what we're looking at? The centerpiece is the shape of an opened umbrella, and decorated with a pixie-like creature:
And several of the girls are holding sticks with the same sort of creature on the end:
Who / Where: If we know which Pack we're looking at we'll know where they are, and vice-versa. Packs first - the annual Education Report for 1922  says:
The Peak and Wanchai Brownie Packs were maintained, and a new Pack was started at Kowloon. The total average enrolment was about 50.
Next year's 1923 report  says "There are at present [...] five packs of Brownies (children under 11)" and lists them as:
- 1st Kowloon Co.
- 2nd Kowloon Co.
- 1st Murray Co. [Children of servicemen in the British Garrison]
- 1st Wanchai
Then a newspaper article from 1926  gives an update, listing only four Packs:
- Garrison School
- Quarry Bay
If no-one recognises the Pack, how about the buildings in the background? Extra clues are the flagpole on the right:
And the grass, which looks as though it is marked out for sports:
- Playle's "Real Photo Postcard Stamp Boxes, A-B"
- Hong Kong Girl Guides' website
- 1922 Annual Report for Education, see appendix G, "Report of the Organising Secretary, Girl Guides"
- 1923 Annual Report for Education, see appendix G, "Report of the Organising Secretary, Girl Guides"
- Page 5, Hong Kong Daily Press, 1926-08-26