Exact item shown: HP / Agilent / Keysight 10793C Laser Head Cable. The HP part number 10793C is clearly marked on the cable jacket and shown in the photos.

This is a 20 meter laser head interconnect cable used with HP laser interferometer / laser positioning systems. Compatible applications include HP/Agilent/Keysight 5517A, 5517B and 5517C laser heads and 5507B/5527B measurement electronics.

Features Souriau circular multipin connectors.

The Keysight page describing this cable is here:  https://www.keysight.com/us/en/product/10793C/laser-head-cable-20-m.html.  Of course it identifies the cable as obsolete (no surprise there).  There is no replacement identified by Keysight.  Keysight says:
The Keysight 10793C 20-meter Laser Head Cable is used to connect the Keysight 5517A/B/C Laser Head to the Keysight 5507B measurement electronics.

Keysight laser positioning systems, utilizing high-quality components, increase manufacturing consistency, improve product quality and reliability, and allow the production of precision products.
There is additional information about setting up HP laser interferometer systems here:  https://www.repairfaq.org/sam/manuals/hobspcl1.htm 

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    A       No Connection on 5517 (MEAS signal level on 5518A)
    B       ~MEAS (Not used on 5517) (2)
    C        MEAS    "          "
    D       Signal Return (MEAS)
    E       ~REF (Zeeman beat signal from internal optical
    F        REF  receiver's differential line driver.)
   G,H      Ground
    J       +15 VDC Sense
    K       +15 VDC
    L       -15 VDC
    M       +15 VDC
   N,P      Cable Shield
    R       Signal Return (REF)
    S       Ground
    T       +15 VDC
    U       Cable Shield
Cable is untested. Photos show actual item and connector condition. Please verify compatibility with your system before purchase.

Note to me: bottom shelf, gray 2-door cabinet

I normally ship within 24 hours of your order, but the post office does not always initiate tracking when I put the packages in the drop off box.  

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