The International Cessna 170 Association

Lubriplate also works well.

Update as promised.
Ended up having a tach that was radioactive due to the type of paint used on the dial and needles, so they would not touch it. Century Instruments sold me an overhauled unit with the identical markings on the face as the old unit, along with setting the tach time to match the old unit. 1 year warranty. $230 plus $20 S/H, including sending the old unit back to me. Purchased a complete new tach cable from Univair. Seems to be working fine. Thanks to everyone for the help and advice.

Radioactive markings on gauges are only bad for you if you lick the face of the gauge or chew on the indicator needles. These are not my words . I have been siting up front in cockpits for over 67 years and I haven’t started to glow in the dark.
Seriously the amount of radioactivity coming off gauges is extremely small. [But my wife tells me I am a bright spark,sometimes]

ghostflyer wrote:Radioactive markings on gauges are only bad for you if you lick the face of the gauge or chew on the indicator needles. These are not my words . I have been siting up front in cockpits for over 67 years and I haven’t started to glow in the dark.
Seriously the amount of radioactivity coming off gauges is extremely small. [But my wife tells me I am a bright spark,sometimes]

Small but detectable. Three guys from my airport bought a Stinson 10A project from a museum in Ontario Canada. On the way home they were met at the US border by CBP agents with shotguns drawn, because CBP had detected the radiation from the original instruments. After a thorough inspection of the trailer they were allowed across, but it was quite the ordeal.

ghostflyer wrote:Radioactive markings on gauges are only bad for you if you lick the face of the gauge or chew on the indicator needles. These are not my words . I have been siting up front in cockpits for over 67 years and I haven’t started to glow in the dark.
Seriously the amount of radioactivity coming off gauges is extremely small. [But my wife tells me I am a bright spark,sometimes]

They basically said the same thing, but they cannot open it because of the radioactive material, so I really didn't have a choice. They told me that quite a while ago, they were not sending radioactive units back to the owner, but that changed after they spent large sums of money to dispose of the radioactive instruments they kept. Not sure if it was some sort of law back then or not.

Somewhere I've got an article that discusses how much radiation is emitted by storerooms of instrument shops and how much time workers are allowed to spend in there (I think it was a defense contractor) due to radium on dials.

Last year or so I visited on the phone with a Coast Guardsman who was a Radiological-Detections Officer in harbors inspecting inbound cargo before the ships are allowed into port. He advised me to contact my state hazardous materials disposal authority (yeah, right) and when I told him I'd simply tossed the dials (of some instruments I'd disassembled for teaching tools) into the residential garbage and sent it to the city dump he let out a lot of fake coughing pretending not to hear. He said that detectors are sometimes placed at large dump facilities to prevent the entrance of such items and heavy fines and back-tracking to the offender is sometimes practiced at large dumps.

Now, I just wear SPF-50 sunscreen or greater and keep silent about such things.