Trade Dress - Only non-functional items can be trade dress, so again possibly headstock but not body shape or anything that has a function.
I'm pretty sure -having dealt myself once with this- that Trade Dress can cover more than just non-functional stuff*. But it can encompass more intangible stuff, yes...like the 'vibe' you're trying to convey with your product.
Basically if you (re)create something that really looks like a well established brand's style with the intent of fooling buyers that they're getting the 'better known' version, you could be sued for that.
Simple example: if you create a soda drink (brand), that's dark brown in color, you make the bottle's label bright red and there's a swirly white, classic font with a flowy ribbon around it, that could be seen as trade dress infringement, even though you may have come up with your own recipe (so no worries about potential, 72-years-too-late and wrongfully applied copyright claims there
) and are not using the name 'Coca' anywhere (=no trademark infringement). And since using a patent, means it expires after 20 years and the contents become public domain, these companies usually don't go that route and prefer to keep their recipe a secret. So (hardly) no worries about patents either. Which leaves trade dress infringement.
And given the long time *and* the fact their patents expired *and* the fact Fender actively promoted the existence of copies/clones since the 70's, *and* the fact that a Silver Sky for instance isn't fooling anyone that they're getting a (copied) Fender, making a case for trade dress infringement will be next to impossible too.
EDIT:
* The caveat in the definition is that non-functional means in this case something else than a passive part in itself...
Trade Dress Protection can be extended indefinitely.
Key Conditions for Ongoing Protection
To keep trade dress protection alive, it must continually meet two core criteria:
Source Identification: The visual appearance must signal to the consumer exactly who makes the product.
Non-functionality: The trade dress must be purely aesthetic or decorative. If the design feature becomes strictly necessary for the product to function, protection is lost.
Back to my soda example: the red label with white swirly font for a dark brown soda sure as hell signifies or suggests a source of manufacture.
And the logo style and the label itself are not necessary for a bottle to 'work', hence the non-functionality. So yeah, Coca co. definitely can protect their trade dress with this. Maybe Fender could've done the same... 72 years ago.... maybe not.
