stumps

So, it would appear that if you have an SW-503A speedometer, it is radium. I have tested my SW-503C and it is definitely not radioactive.

Safety wise, the radiation is not really a problem. It decreases rapidly as the distance from the gauge is increased. Get a couple of feet away, and you won't be able to measure anything with a geiger counter. The problem is the dust from the various decay products of the radium. You don't need extra radioactive sources embedded in your sinuses, or bones, irradiating your body tissues for the rest of your life.

Thanks for the info!

-Chuck