GillW, you are really incredible. I saw this in London and I really thought about you, but you can be right, because this is not a style of brooches the Queen chooses to wear and for that reason not seen very often. So, the best thing is to call the brooch "Lancaster Brooch", perhaps it is also something like "Ladies of Lancaster", like we saw it with the Ladies of Surrey brooch, ...
And if she has worn the brooch on visits to the region, it can be that it is associated there. But I am only since 2009 listing the outfits and the jewelry, so I can not know what she has worn with what on occasions in the past, as you can. I only can recall whether she has worn something before or not.