Did Tom actually tell you that's where he got the information from? If so, then fine but if not then it is pure speculation on your part although maybe based on some knowledge like most things are, or should be, as opposed to just saying it just for the sake of it.
As to the term used on the guide, if it was just an item made for Victor then it shouldn't really be on the guide under Playboy casino as it may not be a Playboy plaque per se.
Knowing what Victor was like according to many, he was pretty flash so he probably showed it off as often as he could. Can't say I blame him.
Of course we can't totally discount that £100,000 don't exist but it still makes me think that the 2 plaques were mixed up together in Tom's description and I think I can separate them enough to make 2 more plausible stories out of the things that we now know.
Using a plaque with diamonds in would have been asking for trouble really as it would just take 1 diamond to be missing which makes it not the sort of thing that should be carried around a casino so yes, it may have been kept in the cash desk as window dressing but Victor possibly owning it makes some sort of sense. Then it would also not necessarily be known by the gaming board as you keep asserting which if it was an actual casino plaque would be doubtful as explained previously especially as he most certainly would not be daft enough to show off.
The Clermont plaque was used many times as some of the staff have said (although probably not often enough to merit plastic ones).