If you bought the Speedmaster years ago, sure, you can definitely make some money on it - but you always have to remember that selling a single watch with no storefront or retail presence for maximum profit is not as easy as one might think. And you won't be able to sell to a retailer for anywhere near the price they will sell it for. And if you are buying today at the inflated prices on Chrono24, then you will likely lose money.
The whole concept of buying watches for investments really turns me off, and drives the crazy inflation in the market over the last few years. I use my investment dollars on buying stocks/bonds on a monthly basis, regardless of whether the price is high or low. In the last 12 years, I've averaged a 10% annual return. I'm perfectly content with that.
My watches come out of my "fun" savings -- the one I pay into for trips, new cars, etc. In other words, for items that will depreciate or have no value after I spend it (like a trip). If I make money on the sale of a watch I decide to get rid of, great. But I don't stress about it either, because I've already assumed I won't.