K.O. is right on the money. One other way to identify Ludwigs from the early 80's until 1983 is the placement of the bass drum badge. As Kevin mentioned, the modular mounts came out on the early 80's probably around 1981. That big triangular mount on the bass drum forced Ludwig to have to move the bass drum badge from the front of the bass drum to the back. Even though this set has the 70's style double tom mount, Ludwig geared up production for all bass drums to have the badge at the players side. Ironically they never moved it back towards the front and to this day the badge sits at the players side(which is something I have always hated).
My only complaint about my classic maple set from 2012 is that the bass drum badge is at the back. I even asked if they would move it and I was told no. I have heard that you can request it at the front now but I am not positive about this and all the new sets I see from Ludwig still have the badge at the back.