It is Bennett 4R mechanism (not spherical 4R mechanism)
4R: 4 revolute joints. It does not meet Kutzbach criterion.
The conditions that the mechanism must satisfy to be able to move:
1. The opposite sides of the mechanism (i.e. links that are not concurrent) have the same lengths, denoted by a, b.
2. The angles of twist are denoted by A, B and they are equal on opposite sides but with different sign.
3. The link lengths and link twist angles must satisfy the relation:
sinA/a = sinB/b
For the blue and yellow (fixed) link: a = 17.599, A= 15 deg.
For the orange and green link: b= 34, A= 30 deg.