Thanks guys, I'm very pleased with it. Despite (the ever more frequent) exhorbitant postal charges from the US, it was still a bargain. I found it buried in the bowels of a non-weapon related eBay category (I love the hunt)
Detlef, the condition is how I received it from the seller. Someone did a reasonable polishing job without doing any damage (which is a surprise) although the brass is over cleaned IMO. I have not etched the blade yet (still practising my technique on lesser items) but it does show signs of lamination. I will etch it and a few others when I am confident not to make any serious mistakes!
Robert, yes the blade has a proximal-dorsal flattened spine (around 3-4cm). I have attached an image of it (at top) with two other similarly shaped blades. I have been pondering on this flattened section of blade for a while: could it's relative size be an indicator of age? I have a feeling that for earlier Gunong this section is quite long (on my oldest it is 7-8cm), reducing to non-existence post WWII. Just a wild thought from a novice.
Thanks again,
Russel