I know その is a noun modifier like この and あの and that の can also be possessive.
So would something like そのとけい mean “That watch you have” or “That watch near you”? Or would it be “Your watch”?
Or is it only “Your watch” if you say something like “そのとけいはピンクです”?
If you want to think about it literally, and if we are just talking about references to physical objects (abstract references to その, この, あの, etc in conversation can be different), then そのとけい means “the timepiece nearer to you than to me”.
It could belong to the person and be on their wrist, or it could be in their hand, or it could be on a table next to them, or it could be a clock behind them… but that’s all that is expressed by その and とけい.
Nothing about this sentence changed the way そのとけい is being used. It’s still “the timepiece near you.” If you want to literally say that it belongs to them, you need to use a pronoun or their name, which you would attach to とけい with the possessive の.
These are pre-noun adjectivals, they are not the same as the の in a possessive sense.
Say I wanted to talk about “Your timepiece”(Leebo’s timepiece).
Would I say something like リボのとけいはピンクです ?
(I’m not sure on how to say it without an adjective)
I haven’t learned あなた yet. I just started working on grammar today.
I’ll have to look into it more to find out what it means. So far, I kind of get it from the context of what you wrote.