I tap tested ISCT1 while the arm was locked. The broad peak at about 71 Hz was associated with the red/green periscope, but the sharp peak at 67.9 Hz did not appear to originate on ISCT1. The tall supports used to dress some cables had similar Qs but slightly different frequencies. The tight ones should probably be unscrewed slightly to damp the flag pole resonance and lower their Qs, but they were not the source.