Found this info at RugerForum.com • View topic - Differences in pre-ban and new Mini-14 magazines?
There is no difference in the 30's between pre-ban and post ban. Both look the same, and have RUGER stamped on the side and the Sturm-Ruger Mini 14 baseplate.
To my knowledge, there are 4 different 20's.
1. The original 20 which was a cut down 30, that had RUGER on the side, and a funky baseplate with 4 pins that hold it on. I'm not sure what the baseplate says on the bottom, if anything at all?
2. The 20's that came out in the 1980's said Sturm Ruger and Company, Southport Conn USA on the side. These have the Sturm-Ruger Mini 14 baseplate with the eagle.
3. The LE marked one's. These said Sturm-Ruger and Company, Southport Conn USA on the side, and right below that, it says: "RESTRICTED LAW ENFORCEMENT/GOVERNMENT USE ONLY 91494" These have the the Sturm-Ruger Mini baseplate with the eagle.
4. And lastly are the new 20's. These say Sturm-Ruger and Company, Southport, Conn USA on the side, but the font is different than the other 20's. These have the Sturm-Ruger Mini 14 baseplate with the eagle.
There is no difference in the 30's between pre-ban and post ban. Both look the same, and have RUGER stamped on the side and the Sturm-Ruger Mini 14 baseplate.
To my knowledge, there are 4 different 20's.
1. The original 20 which was a cut down 30, that had RUGER on the side, and a funky baseplate with 4 pins that hold it on. I'm not sure what the baseplate says on the bottom, if anything at all?
2. The 20's that came out in the 1980's said Sturm Ruger and Company, Southport Conn USA on the side. These have the Sturm-Ruger Mini 14 baseplate with the eagle.
3. The LE marked one's. These said Sturm-Ruger and Company, Southport Conn USA on the side, and right below that, it says: "RESTRICTED LAW ENFORCEMENT/GOVERNMENT USE ONLY 91494" These have the the Sturm-Ruger Mini baseplate with the eagle.
4. And lastly are the new 20's. These say Sturm-Ruger and Company, Southport, Conn USA on the side, but the font is different than the other 20's. These have the Sturm-Ruger Mini 14 baseplate with the eagle.