This is the ACR2 Autochange Rack RBE:  A-1383-0005-RBE.

ACR2 can store up to six probe extensions or probe adaptors. Its modular construction and simple operation enable any number of racks to be positioned on a pillar anywhere within the machine’s volume.

The rack is passive, all locking and unlocking of adaptors and extensions is done by the motion of the CMM.