Welcome to Pistonheads, afraid a lot of posters on here don't like Tags. I can't comment on investment gains on one. My advice is to buy the watch if you like it.
If it’s branded TAG Heuer, then even if there were only 25 pieces, they still wouldn’t be worth a punt. Branded only as Heuer, there’s a slim chance they would hold their value better.
Buy it if you like it, but not for an investment.... There will be much better places to temporarily store ~£3k if that's the main aim. If it has to be a watch then presumably something aged and timeless but anything is going to be a risk.