I took the metal PMC box and examined its content and find the following items:

There seem to be enough parts to build 2 PMCs + spares.

I find several problems in the metal PMCs:

PMC1 has a broken screw in one of its flat mirror mounts (Attachment 16). We need to get it out in the machine shop.

PMC2 one of the flat mirrors has a scratch on the AR coating and its ORing is failing (Attachment 17). Mirror and ORing need to be replaced.

I measure the physical dimensions of the PMC with the help of https://dcc.ligo.org/LIGO-E1400332. The roundtrip is found to be 24cm which gives an FSR of 1.25GHz.

I use Evan Hall's Python script for calculating the mode spectrum as a function of the cavity length of the metal PMC and overlay the RF sidebands (Green dashed lines) on it (Attachment 18) to check for any HOM coincidence. The width of the lines is the mode splitting due to the cavity astigmatism.

It seems like the only issue might come from a 10th order modes (green ribbon) which are hopefully small enough in reality.