Like every kind of object in the world, there are collectors for thimbles. Of course, that crowd is going to create new collectibles for their own delight. If you asked me, I would have denied it, but I guess it makes a kind of sense that someone would create sci fi thimbles.
There's no year on the Dalek thimble. My guess would be the late 70s when the show was seeing a tremendous surge of interest thanks to Tom Baker's portrayal. The thimble is genuine ceramic, with a little gold trim on it. I could see it being a cherished little thing for someone's collection back then. The Dalek is slightly misshapen, as they often were in merchandise. They're such a weird shape, especially if you're barely attention.
The other thimble is even odder. It's just cheap cream-colored plastic. There's a very cheap-looking stamp of Max on the front, with "COKE" listed four times on the obverse. In red. In an unimaginative typewriter font. Clearly not an official product, instead clearly a cheap and odd cashing in on the late 80s fad. Which makes it all the more lovable.
I do love these two thimbles at the front of a shelf in my office. To me, they represent the breadth of sci-fi thimble making technology (as far as I know - I've got a lot more research to do). Not only can you show off your science fiction allegiances in your sewing basket, but you can tell everyone that you have your very own Dalek that helps keep all the little pricks away.