At LHO, the two steering mirrors in front of the POP sled are IO mirrors. The 90/10 BS to attenuate the light on the QPDs has been installed during the June/July 2014 vent.
Pictures of the HAM3 sled are here: https://ligoimages.mit.edu/pages/search.php?search=%21collection1182
and here:
https://ligoimages.mit.edu/pages/search.php?search=%21collection1184
Pictures taken after the BS installation are here:
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