It's by no means a revolutionary design. I don't have photos of the patterns, as they're now owned by Port Townsend Foundry --I had an arrangement with them for a while where when I built a pattern for Bucephalus, if it was a broadly-applicable piece of hardware, they'd trade me the finished casting for the pattern-- but here's a photo of the gooseneck itself:
Very basic three-piece: a pad on the mast with two tangs, a knockle that serves as a U-joint, and a two-tang boom-end fitting, rivetted in place. The eye-nut for the tack is a standard, off-the-shelf PTF eye-nut.
Her original gooseneck was much the same, but brazed up out of fairly light silicon bronze plate, and it had started to deform and was heavily worn. I patterned the new one a lot heavier, and had it cast from aluminum bronze (insanely strong), so I don't think it'll go anywhere anytime soon. The original was also pretty clunky, so with the new one I added some curves here and there and made sure all the edges were nicely bevelled.
The mast band I originally envisioned incorporated little wings as bases for halyard turning blocks, to replace the ABI cheek blocks you can see here. It was also a one-piece, Herreshoff-style, like a big hose-clamp, with a pair of bolts on the forward face to tighten the whole thing down around the mast. I changed approach, back to a pad, because I realized that I was trying to make a single piece of hardware do too much, and it was getting clunky. Your approach, quite happily, does not show such tendencies.
Alex