YES! Thanks to all of you for both an answer and a context.
Tapioca Dextrin: You got it! That’s what I have, except its one double. It has the three griffins (?) on the other side and the color is exactly right. No doubt about it.
Also, the general information on Channel Island coins is interesting, and the idea that it might be a token was a good guess–we have other tokens my great grandmother saved over the years, one for a general store in a gold rush town on the Yukon (Circle City). I have a collector trying like mad to buy that one; he’s says its unique.
As far as the use of outdated coins as non-legal tender in England: In France, in 1970, I found some of my coins turned down regularly, when I laid down a handful, until I discovered they were cheap pot metal from WW II, Scrip from the Vichy regime, I think. I had, of course, received them as change in other transactions. Sharp practice against ignorant foreigners seems to be common in Europe.
Thanks again; I researched this coin online years ago and got nowhere. I even asked a coin collector in England who was the relative of a friend, and he knew nothing about it either.