Who it reaches
On this page11
The jurisdictional hook
The provisions reach articles deposited in the United States mails or transported between states. Selling online and posting a parcel is squarely inside that.
Which catches the whole modern craft market
A bench jeweller selling through a marketplace to buyers in other states is doing exactly what the statute describes, however small the operation.
The duty attaches to the person applying the mark
Not to a manufacturer in the abstract. If you stamped 14K on it, the trademark requirement is yours.
And stamping is optional
Which is the part people miss. Nothing compels you to put a quality mark on a piece. The requirements attach once you choose to.
So an unmarked piece is a lawful piece
Sold honestly and described accurately, with no quality mark, it raises none of this. That is a legitimate choice for a maker who does not want a registered trademark.
But describing it is a different regime
What you may call a piece in advertising and listings is the FTC Jewelry Guides at 16 CFR part 23, which this property does not summarize. Stamping and describing are separate questions.
The trademark has to be registered or applied for
Within thirty days after an article bearing it is placed in commerce or imported. Or you use your name instead, which is the simpler route for a small maker.
Thirty days is short
It runs from the article entering commerce rather than from when you got around to filing, which means the filing has to be part of the launch rather than a later tidy-up.
Multi-part articles have their own requirement
Parts marked with quality indications matching in pattern and size, in lettering at least as large as the quality mark. A clasp marked differently from the chain is the failure this addresses.
And then there is the box
Which is the provision that makes this a packaging property, and it has its own section.