The yahoo group is called "Vikingsewingmachinespre1980" that has a lot of information. They have a list of the models and when they were built, the 21 was produced from 1961-66. It also says that it would have the reduction gear (pull out the bobbin winder knob, it will engage the reduction gear for full power at 1/5 speed).
I have a Viking 6020 (built 1969-72) that I love and have especially because of the reduction gear. My husband does black powder shooting and rondevous reenactment. He makes a lot of stuff with canvas and wool-type fabrics. this machine is his go-to machine because it sew the heavy stuff with this gear. The old 6000-series Vikings are great machines but have a serious flaw, the internal cam shaft. In most of them, it has cracked and needs to be replaced (a $250 repair if you can find someone who knows how to work on them). I got my 6020 for $5 at a thrift store after I pointed out the cracked cam. Fortunately I know someone in the Portland area who works on them and has lots of spare parts. Viking no longer makes the replacement cam shaft but there is a good aftermarket one. It didn't come with any of the attachments but a few months ago I found the accessory tray with the attachments at an estate sale for $3 and did the happy dance!
Last edited by Skyangel; 10-15-2012 at 04:06 PM.