It looks to be a LJ60. Like all classic Learjets, the stall characteristics are governed by a "stall strip" only about 6 inches long between the fuselage & the wing fence. This must be adjusted by hand after a qualified pilot conducts the initial stall testing. My guess is that this is a video of that initial testing.
For an illustration, google "learjet stall strip" and you'll see the device in "Flying the Classic Learjet".