Hi Ray,
The industry standard is, regardless of builder, the designer pedigree takes precedence. For example, all J24's are considered J24's regardless of who builds them. From Wikipedia:
The J24 designed by History[edit]
In the summer of 1975 Rodney Johnstone designed and built hull number 1 in his garage in Stonington, Connecticut. "Ragtime" would serve as the master mould for the subsequent hulls. This design allowed him to start the very successful J-Boat company with his brother Bob Johnstone. By 1978 the class was popular enough to hold a one-design regatta in Key West with twenty boats on the line.[citation needed]
Early boats (hull numbers up to 3000) need a lot of work to rebuild their keel shape (move material forward) to make them point and sail fast in light wind. These older boats can be modified if one wants a competitive J/24. New boat manufacturing is done by multiple companies around the world in France, USA, Italy and Argentina.[9] In the US, J/24's are built by US Watercraft.
As of January 2009, approximately 5,475[10] J/24s have been produced. Approximately 20 new boats were produced in 2008. The average price of a complete, new boat without sails was approximately £20,000. (31,370 USD)[10]
No one would dispute a J24 built by US Watercraft is less of a J Boat than an original.
Interestingly, HMCo developed a reputation as a builder so that many boats designed by others and built at Herreshoff today, are lazily called a Herreshoff rather than an Alden built by Herreshoff or Herreshoff-built Burgess. Some like the MIT dinghies, designed by Owen, are now just "Tech's".
Wouldn't worry about it too much. The boats with the builder's plates are real Herreshoff.
Far less fortunate in providing provenance of origin are those with boat's whose builder plate has been removed.
-Charles