for sale: factory originals 1)HP5253B Frequency Converter: 50 - 500mhz plugin for HP5245 mainframe; Op/Service manual, serials prefixed 513-; two available $15.00 + ship 2)BIRD Model 43 Wattmeter Instruction manuals; $15.00 + ship please email replies, tnx in advance barry carson city, nv http://home.att.net/~btuttleman2/electron.html