Probably useless today, but what a cool bit of autopilot nostalgia! A mechanical gyro from a missile for $16.95. From the product listing: "These are precision rate gyros that were made for use in guidance systems of military missiles. The last time we had these we were told that they were from the Maverick Missile Program, however, we don't know for sure. They were made in 1981, they are new and were made by Honeywell. The part# is 3051235-1 and the model number is GG440A18. They are 2 1/4" x 15/16" Dia. The body is gold plated and the gyroscope has 6 color coded flexible wire leads. We supply it with a circuit diagram showing how to use a 741 Op Amp, a 2N3904 transistor, a 2N3906 transistor, and a few resistors and capacitors, to cause the internal gyro motor to spin from a 400Hz signal that the circuit produces (the circuit requires + and - 15VDC). The circuit shows which leads of the gyro to use to spin it, however we don't have any other data. We were told that the phase angle output changes as the gyro is tilted, This gyro was known as the Golden Gnat and we were told it was used in autopilots, missile guidance and robotics. Hurry these will sell quickly!"
(via BlueSky on RCGroups)
Update: more on the history of this gyro: