One of the 135 bronze medallions of the "Hommage à Arago"

To commemorate Arago an 'invisible monument' was created by Dutch artist, Jan Dibbets, in 1994*. Ostensibly it consists of 135 bronze medallions, each 12cm [4.7"] in diameter, inlaid into the ground along a 9.2km [5.7 mile] stretch of the Paris Meridian Line. I say 'ostensibly' because whilst the 'official' documentation about the monument states that there are 135 medallions, their own Arago Medallion Location List only details 120 items.