This is a DB15 to BNC RGB color monitor monitor cable for a Digital DEC Vaxstation 3100.

I have tested all of the pin outs as described in the screenshot and continuity is as expected for our, g, b and shield.

I do not have a DEC VAX station to test this with, but hopefully that helps.

This is a high quality cable with heavy construction. You can feel the toughness of the shielding and the three breakout BNC cables.  It appears to be in good condition and I see no damage to the cables or the strain reliefs, but there are signs of use.

Hope you can use it. Thanks for looking.