I picked up another one of these today to assemble and to see if I could decipher the puzzle.
Each arm section has a small number stamped on the side of it: 1, 3, 4, 5, 6, 7 and 8. There is no number 2.
Here's how mine assembled starting from the arm in between the blue and red vial piece and going around counter clockwise.
6 - 4* - 5 - 3 - 8* - 1 - 7
*arms with sections permanently installed in body.