To start with, the blue sky and the lamp fixture indicated that this was an active lens, not one in a museum. The uniform prisms in the upper section, and the middle section on the left that resembles the picture above it ("beehive" style) meant that this would give a steady light, but then the "bullseye" flash panel meant that it would also give a periodic flash (assuming it's a rotating lens, which was a safe bet). That's an unusual flash characteristic; most lenses either give a steady light or a flashing light (like the first lens picture), but not both. I could also make the assumption that this is a lighthouse open for tours, and the lens is clearly large; probably second-order at least, and I was guessing first-order.
So, active lighthouse, open for tours, still using an antique lens, probably first-order, and with a steady light that also has a periodic flash. That narrows it down quite a bit. We also know that they were last seen heading down the east coast. A good resource for that is
https://www.unc.edu/~rowlett/lighthouse/
although for other sorts of searches Nancy prefers
http://www.lighthousefriends.com/
The UNC site, for example, turns up the previous two lighthouses as featured pictures for the state they're in. I could have just scanned down the east coast, and the light characteristic that I described would have popped right out. But I got lucky before I got that far. There were some other lights that had characteristics that looked like they might match what I was looking for, so I did a Google image search for "XXXX lens", substituting in the name of the light in question for XXXX. That allowed me to rule those out, because the lens wouldn't look right, or the lamp fixture would be wrong. For example:
But searches like that will turn up miscellaneous stuff, and in the course of investigating a light that was still north of there, I stumbled across (I think) this picture:
And I knew I had it. Looked for more lens pics of that light to confirm it, and checked the characteristic and other info on the UNC page, bingo. Took 5-10 minutes, mostly on my phone. Might have been less if I would have guessed they were driving so fast.