Having been through the patent wringer successfully, ignore the pretty pictures and read the claims. The claims are the beating heart of a patent; they are the legal limits to what the patent holder can ask the courts to enforce. If it's not in the claims, it is not an enforceable element of the patent. Reading and understanding the claims section of a patent is the key to understanding whether or not any element of Manzer's configuration is her intellectual property.
Smith's claims:
1. In a guitar, the combination of: a body having a front surface and a rear surface, a neck extending from one end of said body, said body being approximately wedge-shaped in cross-section transverse to the length of said neck, to form a thin side and a thick side, strings tensioned over the body and the neck inclined in a common plane, so that the thin side of said body may fit under the arm of a standing musician, with the plane of the strings inclined downward and away from the musician.
2. The structure of claim 1 in which the body comprises a hollow acoustic shell.
3. The structure of claim 1 in which the plane of the strings lies at an angle to said rear surface.
4. The structure of claim 1 in which the plane of the strings is parallel to said front surface.
http://www.google.com.pg/patents/US3426638The question is NOT whether the patent drawing looks like Manzer's 'invention', but instead whether Smith's claims perfectly describe the elements of a 'Manzer Wedge'. Are there any claims which do not apply? Any missing? No - the claims perfectly describe the configuration. And if the claims describe the configuration of Smith's invention, it is most certainly NOT someone else's invention.
If Linda could propose another set of claims which described the wedge body but did not overlap, there might be a case for some degree of unique IP, but I don't see anything not fully covered by Smith's claims.
Mark - I'd be very surprised if this has not been discussed, but given the patent expired a year after Manzer started offering the feature, any enforcement action by Smith is outside the statute of limitations. Beyond that, it's an ethical issue, with most people being unconcerned or disinterested in the specific and the more general topic. Finally, there are few things more difficult that intellectual honesty when it concerns people we either care for and like or those that have earned our disfavor.