Hi Dave,
This is truly a fascinating item & has me in the same quandry as you. If it was purely a "one off" I'd say that someone has taken a standard Pattern No. 7 Privates tool, drawn out the oil pin under heat & formed the "corkscrew" - why? who knows.
There is what appears to be a fold line groove running around the "corkscrew" wire, does this support the idea described above?  
 
However if the recent owner has seen several tools, over a period of a decade, with this same "corkscrew" in lieu of oil pin, then one has to speculate that perhaps it is a rather rare unaltered tool. Though this chap is more of a cork screw collector that a gun tool collector, its also therefore not impossible that he is mistaken, saw the worm on the arm & never actually removed the oil pin for inspection etc.
 
Of note is that the # 7 pattern tool was approved in mid 1862, right about when the W.D. was into capping breech loaders. These required a tool with a nipple wrench, vent prick, oil & oiling pin, the screw drivers and, ideally, a chamber cleaner. The regular worm was in theory surplus to requirements, however these arms could be used as a muzzle loader in case of emergency & so worm retention could be justified. Could the "corkscrew" have been intended as a chamber cleaner for such a gun? As pointed out, it would still function as an oiling pin as well. It is rather small in diameter for the chamber calibre (one has to assume .577 based on the attached regular worm diameter), but it could have easily been wrapped with extra cloth or tow to do the job.
The Westley Richards "Monkey Tail" carbines in the service were issued with a specific tool (well documented though I have yet to see one that conforms exactly to the L.o.C drawings) and also with a separate device for cleaning the chamber.  
It is not impossible that the tool shown here is perhaps a limited issue item superseded by the Westley Richards tool, or perhaps was used for one of the other capping breechloaders in limited use.  
 
Centrefire cartridge arms did not require this configuration - as transpired on the undocumented "Snider" tools which survive in modest number. �
 
It was listed by the owner as a pistol tool, & if so the corkscrew could have been intended to draw charges from a short barrel, or to clean same. But I don't think this is the case. About the only thing short enough for it to access would have been a revolver's cylinder. Two types of percussion revolvers were issued (three actually, the Adams was in two calibres). One, the Colt Navy had an entirely different nipple wrench & no need for the regular worm etc. Two, the Beaumont Adams, its nipples could not be removed by the regular issue nipple wrench, requiring one slightly smaller & of which I only know of one sample, & which happens to be Enfield & WD marked.  
I can't think of any use for this "corkscrew" on an ordinary percussion pistol, no more than I can on the P/53 family of carbines & rifles etc.
 
The mystery I suspect will turn largely on whether or not other examples have been seen.
 
My thoughts
Adrian
 
 

Hi Bill,  
I had assumed that the presence of Enfield inspectors marks on the parts in question would mean that it was not a commercially made item, its not good to assume I know, but is that not the case?
Regards,  
Adrian.