I looked up R-class sloops, and that is certainly a nice vessel. The sloop they highlighted in a few scenes were similar to style to the R-class, but not an R-class. ....I'm still wondering if anyone knows.
I don't know if anyone has mentioned this, but I thought I'd say my 2 cents. I don't have an answer per say, but I do want to suggest YahooAnswers. They have saved me in so many pinches. Might want to give it a shot.
To NK235: Were you just as enamored with that boat as I was while watching it? It's funny, I actually stopped listening to the film, and was just thinking, "...now what kind of boat is that?...Brad, get out of the way, I'm trying to ID the boat." Maybe this means Brad Pitt is no longer my number two celebrity crush (Depp is #1), and this boat has taken his place.
To CapnRon47: It had similar lines, but was much much smaller. It was somewhere between the boat in your photo, an R-class, and a Pearson Triton.
I should have taken a screenshot of one of the scenes, but i only rented the film so now I can't.
...well, maybe there's someone out there that knows.
I was only able to find a thumbnail photo of the boat from Benjamin Button, my first guess is a Lawley built S&S Designed Dark Harbor 20 (31 feet overall) if this is a small boat or else the picture looks like a Starling Burgess designed 8 meter that I once knew named 'Cuyuga" which was around 42 feet. I would also suggest that the boat in question could also be an International one design Class, a Scandinavian designed 5.5 or six meter, or else the only remaining 'Resolute' class. What ever Button Up is, she was probably built under the International Rule and would think this probably a Scandinavian design rather than an S&S design unless she was penned by Aage Nielsen while he was there.