The gemara says that a slave is allowed to go out with a seal that he's a slave, the only problem possible is that it might fall and he would pick it
up and come to carrying. But, the fact that he's wearing it is not a problem, even though it is not an ornament as Rashi explains- to the point that he's even embarrassed of wearing it. Isn't this proof that one is allowed to wear a wrist watch on Shabbos without worrying about the problem of carrying even if it's not gold?
Shemiras Shabbos keHilchasa, Chapter 18 #27, write that there are valid grounds for wearing a wrist watch that is not gold in Reshus haRabim. He cite Rav S. Z. Auerbach zt"l as saying that wearing a watch is Derech Malbush as everyone wears them in this way at all times. Also, It is not necessary to remove a watch to make use of it. According to this your observationis correct that just like a seal of a slave is Derech Malbush for him so a wrist watch is Derech Malbush for most people. Kol Tuv Ilan Segal