That is a model 64, which is the stainless version of the model 10 heavy barrel. The barrel length is 4" as measured from the face of the cylinder. There have been quite a few of these police trade-ins surfacing in the past few months and the prices vary by condition. From what I can tell in the photos, your looks to be in better than average condition. Most of these guns were carried alot and fired very little. It will handle any +P 38 special round. An extremely solid gun for your intended purpose. The sights are a little sparse for fine target work, but once you find a load that is regulated to your sights you can hit anything all day long. Welcome to the forum and enjoy shooting your new gun.

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Tony