Hello, Please be kind as I'm new to handgun ownership. I'm looking to purchase a very good condition glock 23 2nd generation from a good friend of mine. He informed me that it has something called a secondary frame on it, and to be honest I don't know what that means, so instead of being embarrassed by one person, I figured it was a good idea to be embarrassed by potentially millions of people on the web. I'm just curious what this means, and want to make sure that this will still be a legal firearm to carry with my new permit in the law's eyes. Thanks for all of your help.