Actual FOV of standard lens

Question

I have an A33 Jevois camera with standard lens. I'm trying to use this camera for mapping/SLAM purposes, so I need to get FOV relatively accurately. Checking online, there appears to be conflicting specs on this, where the FOV is stated as either 60^o or 65^o (here http://jevois.org/doc/Lenses.html and here https://www.jevoisinc.com/pages/hardware).

I decided to take the camera to the Vicon motion capture room to see if I could validate either of these figures.

I calculated the FOV by determining the horizontal length a known object was in the camera image, then knowing exactly how far away the camera was from that object, I could calculate the FOV. The figure I kept realising was just shy of 51^o (well short of the 60^o - 65^o).

Have you guys done any testing to determine the effective FOV of this device?