I did a quick web search and found
this page. There are a bit of info to be found on the web. For dating you need to identify model, and maybe some have a few details on serial numbers. There's a good chance of it being over 100 years old, which generally is the age where an item can be called an antique. The name was still used after 1920 so not all of them are strictly an antique yet. As I'm sure you know, vintage is a rather loose term, and I'm not sure any strict definition is set. I have seen a few magazines try to define the vintage trend in clothes and fasion, but you can largely adjust the term to suit the sitation. There are Damascus rotary models as well as long bobbin VS models.