Well, you pick your choice here. The record will probably remain somewhat unclear:
"At about this time (fall of 1864), I had a desire to have a boat, and I designed and made a model for a 16 ft. cat boat. This was not built then, but the following year for a Mr. Holden and was named HENRIETTA. [It was owned] later by Charles F. Chase [and] named POPPASQUASH." (Source: Herreshoff, N. G. "Boats and Yachts that I have been Especially Interested in by Sailing and Some of Which I Have Owned." Bristol, April 1932. In: Pinheiro, Carlton J. (ed.). Recollections and Other Writings by Nathanael G. Herreshoff. Bristol, 1998, p. 103.)
"This year, 1865, John built two boats from my models, my first to be built from. They were the sixteen foot catboat POPPASQUASH that was owned by Charles Chase Sr. for many years, and the sloop yacht HAIDEE, about twenty-seven and one-half feet overall. I sailed quite a good deal in each of them and they proved very good little craft." (Source: Herreshoff, N. G. "Some of the Boats I Have Sailed In." Written 1934. In: Pinheiro, Carlton J. (ed.). Recollections and Other Writings by Nathanael G. Herreshoff. Bristol, 1998, p. 46-47.)
"Following the model for the 16 ft. boat [HENRIETTA / POPPASQUASH], I made a model for a 25 foot sloop HAIDEE for Dr. S. Powell, 27' oa., 10'9" beam. After selling, [her] name [was] changed to FANCHON. This yacht I sailed a good deal in 1866." (Source: Herreshoff, N. G. "Boats and Yachts that I have been Especially Interested in by Sailing and Some of Which I Have Owned." Bristol, April 1932. In: Pinheiro, Carlton J. (ed.). Recollections and Other Writings by Nathanael G. Herreshoff. Bristol, 1998, p. 103.)
"This exploit [of leading for a while during the 1865 the New York Yacht Club Annual Regatta] brought John [B. Herreshoff] and [Dexter] Stone to the limelight, and in the year (1865), they built HAIDEE I, a number of small catboats and fishing boats, besides a large number of cheap yawl boats to be shipped to South America. HAIDEE I, a twenty-five foot waterline sloop, was my first design and she proved very satisfactory. She was afterward named FANCHON and went into the hands of Edward Burgess and he won many prizes with her." (Source: Herreshoff, N. G. "The Old Tannery and My Brother John." Written July 28, 1933. In: Pinheiro, Carlton J. (ed.). Recollections and Other Writings by Nathanael G. Herreshoff. Bristol, 1998, p. 22.)