To avoid theft, i always use terms like "professional timing device" or "time keeping mechanism".... Personally, i would avoid using "watch" as it will raise the awareness of thieves.
And regarding taxes, always have you watches insured and declared to the actual amount as watches are tax free in Malaysia.
I have bought and sold watches which would require international delivery for years . So far, touch wood, it has been without any incident. A few things you can do :
i) Have it professionally packed and sealed with multiple layers and boxes- it adds a bit to the weight but international couriers charge by spectrum e.g. up to 10 kgs box etc. It helps a lot if you have a friend on site who can help you with this.
ii) Use courier service (like DHL) and make sure you get it insured for full value with ParcelPro- you need to open an account with them though
iii) Pay with credit card that offers some kind of protection in case of dispute or paypal (for paypal, never agree to pay as "gift")
iv) One of the most important bit is buy from a trusted seller (obtain independent references from sites like TZ, Purist, Paneristi, MWF etc) or in my case, usually from the boutique.
v) I will use the following description : Precision Instrument- return for repair for the airway bill.