A third party is making those knives for Purdey

If you look at the 2 websites, Purdey's 'DEER HUNTER WITH BRASS GUARD' is identical to CSMC's 'Thumb Groove Hunter Knife' aside from the handle's wood and the metal used for the bolster.

https://www.purdey.com/deer-hunter-with-brass-guard-and-lanyard-hole-walnut

http://www.csmcspecials.com/Thumb_Groove_Hunter_Knife_p/k0140.htm

I have the CSMC knife, it's a nice enough knife, but you can get Damascus blanks for under $50.

I have become addicted to English hammered shotguns to the detriment of my wallet.