To be sure gold bracelets are authentic, take your jewelry to a jeweler or gold-purchasing service. Either place should be willing to tell you if your gold is real or not.
Yes, gold bracelets are always in fashion, that is one item that will travel through time and fashions. The other wonderful thing is that gold holds its value.
427? You maybe confusing a number, 417 means 10K gold; that is, 41.7% gold. The remainder is a alloy of silver, copper, and zinc, or in the case of white gold nickle is added in place of the silver.