grizzly60: those adapters are made of steel and usually conform to the first chamber they are fired in, lever, bolt or single. Once the adapter has been used it is sized to that chamber and may not fit another chamber. If your chamber adapter fits a rifle chamber you currently own you have a real prize.
I'm not sure they can be sized down again, being steel but possibly they can. One gun writer wrote, recently, of reloading steel cases found on the range and although the chamber adapters are, by necessity, a bunch thicker than a steel shell casing, they made not be able to resize. Maybe they can be resized is you use a bunch of sizing lube, and this would allow you to use the adapter in a rifle properly chambered.
On the other hand I would opt for a new one and keep that as a collector's item. I believe you can get new adapters from MCA Sports, and at least then you would know the proper adapter chambering. HTH. Mikey.