How much is my HP 435A worth?

Instruments such as these power meters are priced all over the place because of

3 factors. (1) Checked and working, or just plugged in and turned on to see if the pilot light glows. (2) Does the unit include the power sensor (thermistor mount)? (3) overall condition of the unit.

Instruments that are complete with thermistor mount and have been verified to work command a premium price. Physical condition is less important, but clean and unabused indicates that it's lead a good life, and is likely to live to a ripe old age.

Watch Ebay for a while and search for auctions that have already closed to get a good idea.

--
Dave M
MasonDG44 at comcast dot net  (Just substitute the appropriate characters in the 
address)

Make it idiot-proof and someone will make a better idiot.