Jim, you are VERY observant. I bought the gun and have examined the missing pistol grip with a large magnifying glass (playing Sherlock Holmes). Here's what I surmise:
1) The gun definitely went through an Arsenal Repair -- small chip repaired in the butt just behind the receiver ring, new Suncorite, new rubber butt (that sounds obscene!), and cleaned up finish.
2) The stock is definitely 100% authentic -- took the butt plate off, and the interior is exactly like a No. 5 should be (not a converted No. 4)
3) The missing grip may have had been chipped, then the Armourer carefully shaved/planed off the entire grip.
Or an alternate theory: The gun was used by a Sergeant Major who had really big hands and his hand was too big for the gun's wrist.
Experts chime in if you have another idea --see Lee Enfield No. 5 Mk 1 Jungle Carbine #5 : Bolt Action Rifles at GunBroker.com
Robert