Well, mystery solved! It is indeed a Citadel figure and was found in a castings box of Rogue Trader adventurers in Bryan Ansell's collection:
Unfortunately there are no markings on the front or rear of the tab so I don't know what this figure actually is. Any guesses? An inquisitor type perhaps? I'm not aware of any images that portray this figure but some of you may have sharper memories that me.
Another mystery can be found on page 190 of the Rogue Trader rulebook. A strange figure lurks in the top left, and is highlighted in the image below. He looks like one of the Realm of Chaos thugs from the late 80's, but what is he doing in this picture?
Again, the figure has been found in Bryan's collection:
It is indeed that chaos thug and it looks as if he has been converted to carry a weapon of some sorts. Perhaps he's some sort of rogue trader or Imperial augmented humanoid. Any guesses? Any idea who painted and converted this figure?
***UPDATE FROM A PREVIOUS POST***
Someone (thanks Alan) helpfully left a comment on my unreleased Adeptus Arbites post highlighting the similarity between the crouching Adeptus Arbites figure and one of the old Citadel SJS Judges. Here is a comparison pic (SJS Judge pic obtained from the Collecting Citadel Miniatures wiki):
Alan went on to comment:
The other one looks like an SJS Judge from the JD8 blister. My betting is they're either test scuplts for a range that never was, possibly due to the IP issues (not that that stopped them recycling the original LOTR range using the simple expedient of scratching the names and copyrights off the slotta tab...), or perhaps just cast up for an 'in house' game, never intended for a proper release.
Bryan Ansell also left the following comment on the Adeptus Arbites:
I think that they look too scratchy for release. Probably someone knocking up a few models for there own use.
So, that's it as far as "new" unreleased Rogue Trader figures go in Bryan's collection?
Actually, there's more to come...