This is a Watkins Johnson triple balanced mixer with LO and RF port coverage from 4 to 20 GHz.   Its very similar in frequency range to the STDB-2005 mixer. 

Approximate dimensions are .75 inch by 3/8".  It is the standard drop in mixer module size.

You can see some specs on the STDB-2005 mixer at:

http://www.craneae.com/Solutions/Microwave%20Systems/data%20sheets/Microwave_Systems_Components_Catalog.pdf

The IF port goes down very low if you are not concerned with balance.