Hey guys, I'm planning on buying a Glock 21SF, I compared it to several other makes while test shooting all of them also and I liked the SF the most. Now, I did research before I bought one because, well, it's smart. I found that the earlier 21SF's were not able to take the standard Glock 21 mags but the newer 21SF versions take both. My question is, if I buy a used 21SF, how can I determine if it is an older model that doesn't take both mags or if it's a new model? Or, were the mags changed so the older SF will take both now as well. Hopefully that makes sense. Thank you in advance for your help.