A photo is virtually essential for this one.
However the description:
... a star in brown and white and the Y is black
sounds like it could be right. But if it's a definte "star", rather than a "cog" (having flattened ends to the "arms" instead of distinct points) then I might query it.
Click here for an example of a Salvador "Y" cane from one of my own weights.
All of the weights I have seen with a Salvador "Y" cane have been 3 inch diameter or slightly larger. So 2 1/2 inch is interesting.
Also interesting is a "flat base". Does this mean absolutely flat - and smoothly polished? If so, that is unusual.
Rarity? Well, any wieght (or ink bottle, or perhaps some other item) with a Salvador "Y" cane is much rarer than those without. But over the last few years, several more have come to light, including at least two ink bottles with a "Y" cane in both the base and stopper.
Value? Hard to say. It depends very much on the actual appearance of the weight and the type of other canes it contains - and whether it is really a Salvador weight.
A few words, however, on retail prices...
I once bought an unsigned concentric that looks just as good as one of my signed ones. The unsigned one cost me £20. The signed one was somewhere around the £300 mark. But I also set what I believe was a world record ("silly price") for a signed Salvador weight. That one cost a lot more than the earlier one. The main reason I was prepared to pay the extra was because it also had a very rare early Vasart label. But after that, the higher price began to be "the norm" for "Y" weights without a label.
How much is the "higher price"? ... keep an eye on dealer websites and eBay - although not seen too often, they now seem to vary from around £600 to over £1,000! But just because a dealer may be asking a very high price does not mean that anyone will actually pay that much.