Hi Andy, yes, this looks original to me. Near the end of the 60s, Mosrite started cutting corners in a few ways. This is evident with the guitar also having "Diamond Tuners" which were cheap tuners that Mosrite normally would not have - they're supposed to be cheap tuners that won't last as nicely as a set of Klusons or Grovers (Mosrite used both, normally Klusons, but they also used Grovers in the 70s.)
However, the seller doesn't know the year. That's not 1965, this is more like maybe late 1967 / early 1968. It's impossible for it to be 1965 for two reasons: (1,) Mosrites didn't get the truss rod adjusted at the headstock until March/April 1966. (2,) The first Celebrity models only started in Late 1965 / Early 1966, and the earliest models might have been set necks (I don't recall,) but the earliest (within the first 600 to 800 or so) all had a 2 bolt tenon neck joint. This one that you linked has a 4 bolt neck joint. (3,) in most cases I've seen with the "Diamond Tuners" that are shown here, the guitar has a high serial number, indicating the cheap tuners thing was late in the production run.
- Austin