Can anyone shed some light on what this brand might be, and/or give me some pointers to websites etc telling more?
It’s a (not uncommon) brass whistle, lead fipple, pretty quiet (narrow windway) closer to Eb than D actually. Haven’t played it save for a couple of minutes because i will varnish the exposed lead before playing more.
Below are links to pics of the whistle, didn’t want to post images as they are pretty large and i can’t be @rsed to make smaller versions 
Cheers!
https://dl.dropboxusercontent.com/u/1118766/IMG_3497.JPG
https://dl.dropboxusercontent.com/u/1118766/IMG_3498.JPG
https://dl.dropboxusercontent.com/u/1118766/IMG_3500.JPG
https://dl.dropboxusercontent.com/u/1118766/IMG_3507.JPG
As the label says, JH, made in London, Trademark, in tune.
I’d suggest finding the old trademark records will give a clue. I have a bunch of those, B, C, Ds (including a keyed one), they are not uncommon anyway.
I know they’re not rare, they keep popping up on ebay every now and again.
I can’t make out the ‘JH’?!
Trademark, D etc i can read, but i can’t make out the motif.. looks like a bare breasted angel or something, but that might be in my mind 
In any case i am glad i got one.
It’s a version of the Coat of arms of Ireland, a female form as part of the Irish Harp a common heraldic image as far as I know.
The UK trademarks office doesn’t immediately throw up any reference to either the image or the initials but I suppose maybe I searched fairly narrow parameters
I know they’re not rare
I meant this particular make which, out of ones that are branded at all, seems to be one of the more common ones.
Ok, thanks for trying anyway!
Maybe the Generations of that time? Or they co-existed?
I’d say they overlapped although I sometimes wonder if there two or three places churning out whistles and (re-)branding them with the name of whoever was selling them. Which was fairly common at the time (cf concertinas etc).
It would have been easy enough since the ‘label’ is folded around the tube and soldered on the rear side..