the whistle is stamped REGD (registered design) BUKTA - Pretty sure it is made by Alfred de Courcy -
https://en.wikipedia.org/wiki/Alfred_De_Courcy
Body stamps
De Courcy did not stamp whistles with his company name prior to 1906 but prior to this year supplied many orders to railway, Police, Army, Navy, Asylums, Fire Brigades, sporting goods companies, arm distributors and hardware stores as well as for other makers as W Dowler & Sons and B Lily & Sons. Many of his whistles prior to 1906 are easily identified by shape, construction and characteristic designs.
While his business and reputation grew he first stamped whistles A De Coursy & Co. Frankfort Street Birmingham in 1906.
It would be beyond the scope of this page to list all while some are still being discovered by collectors, here are some samples:
Stamped on GSWs:
Edinburg Police, Liverpool city police (Also marked with a crest at back), Leeds Police, Walsall Police, Westmorland Constabulary, W.R.C., Derby Borough Police, Lancashire County Constabulary
GPO General Post Office)
The City Patent Whistle
The City Police
The City Police or Fire Whistle
Boy Scouts whistles (GSW Type) The Scout, Girl Guide, The Boy Scouts, Bukta
Regards
Gary