She may be a Lawley S boat, but I can attest to the fact that Lucky Pierre is in very good shape and is no slower than HMCo. built S boats, having raced against her many times.
Adam, I especially appreciate your mentioning Firefly (hull #956), since I own her, and if all goes well, she will be launched in Newport in 4 days. While Firefly was contracted in Aug. 1925, her HMC hull # plaque says 1926, so I assume she was actually built or completed in 1926. Firefly was the first of 12 S boats built to the "956 Class," most of which went to Bar Harbor, although a few went to Marblehead.
One other bit of trivia-- the Sparkman Stephens ad that you reference has a picture of a HMC S boat (with a carved sheer), not a picture of Lucky Pierre (Lawley S boats do not have the Herreshoff sheer strake).