The earrings Geneva wears with her riding habit are the same earrings Claire wears in Season 2 when she visits Master Raymond in his shop.
Jamie is serving Lord Dunsany. The name is probably a tribute to Edward Plunkett, 18th Baron of Dunsany (1878-1957), an early writer of fantasy, known by the name Lord Dunsany.
At 12:30 as Claire hangs up the phone, a crest can be seen hanging on the wall. The writing in it, 'NEMO ME IMPUNE LACESSET' translates from Latin to 'No one provokes me with impunity'.
According to the official podcast, Helwater exterior is actually Gosford House while Gosford House interior serves as Ellesmere's interior. Gosford is outside of Edinburgh.
Willie's full name is William Clarence Henry George Ransom.