The 8760B Option K73 is a 24 input 3 output switch matrix. I have not been able to find any information on this unit at all. The only 3760B information on the Keysight web site is for the KA8 option and the KA8 is a very different device to the K73. It has what looks like 4-way power dividers and 2-way and 6-way switches. There are no part numbers on the switches and the only number of the power divider is DM54095/SMA. Because of the presence of the power divider I suspect that this is a narrow band switch.