I should imagine that the first blue trail was applied when the vase had an upturned neck. The other trails were applied afterwards and the neck cut to allow it to form its present shape. It's a pretty vase and IMHO (have to say that!) it looks modern.

One indicator of age is wear to the base, it's not a fail-safe indicator as it has been suggested that age-wear can be faked, but it's something to bear in mind anyway.
