Welcome,
As you probably know the niners wore that patch in the 2006 season. Reebok generally didn't put patches on their jerseys, but they did on some, not sure if this was one of the official patched jerseys they made.
Here's the link to the jock tag timeline for you to look at http://www.nfljerseyfanparadise.net/Hemtags-h6.htm
You can see the different styles for the corresponding years, I would expect it to have the multicoloured NFLPA logo on it as this was the style for 2006.