Hi
I’ve got a low G metal whistle that I bought several years ago secondhand, it doesn’t appear to have any name stamped on it.
I’ve recently started to play it and can get a reasonable sound except when I go up into the upper register above G. To get these top notes I have to blow really hard and it sounds terrible, so any advice as to what I should do would be welcome. Oh and also I’d quite like to be able to play like Brian Finnegan - any tips? 
John
I think you need to just work at blowing harder for those top notes. As for playing like Finnegan, learn how to triple tongue.
BTW, your whistle may be an OS (Old Style) Chieftain as I know those do not have a makers mark just the key stamped on them.
I saw a low G on ebay the other day with no name of the maker. I asked the seller who made the whistle and received no reply.
Thanks for the advice Unseen, I have been trying to blow harder without increasing volume - seems to be working.
Perhaps a little trick could help, which worked fine for me: Make the windway narrower by “filling” it lengthwise on one side with a carved small wooden stick, match or any suitable material. It’s also a suitable method to mute the whistle and effects in less blow for the upper registers.
Good deal; that’s the trick. It’s in the diaphram and in the embouchure.
If you can get your mouth and lips (but not your throat) to shrink the
opening that the air goes through before going into the whistle, this will
increase the speed while your diaphram increases the pressure. It
saxaphone parlance, we say “Blow slow, hot air for the lower octave,
and fast, cool air for the upper.”
Look the embedded entry of “Kerry” here: http://chiffboard.mati.ca/viewtopic.php?t=37315&highlight=mute