The upper arms are dated on the nose of the UCA by the ball joint. Not real well and sometimes missing one or both characters!
Later in 68 the metal was clipped in the outer ball joint area to clear wider rims.
In plan view original UCA have a unique shape, different from most repops. The easiest to see is the sharp point the outer metal outline has at the spring pivot.
Most of the repops are softer or almost rounded here.
Perhaps share a pic?