Really good question & answers .
Sometimes it seems more of an art than a science , but I think as time goes on , both worlds ( learned experience & technology ) are coming together to try to verify the authenticity of antiques .
All of the 'fakes' have helped in this field , really .
Science does not always get it right ( and vice-versa ) .
In earlier times , the general 'rule-of-thumb' for defining an authentic antique , the criterion were :
1. The item had to be 'hand-made' (ie - no powered machines used in manufacture , except for human/water or animal powered , and sometimes 'fire-powered') , with few exceptions .
2. The item had to be at least 100 years old .
The industrial revolution came about , and machine production came into it's own , offering 'mass produced' products .
This allowed people worldwide to own many items that were previously limited in production and manufactured by 'artisans & craftsmen' .
Nowadays , we're seeing alot of these machine produced items classified as antiques , due to the fact they are 100yrs. old .
Look around in most any 'antique shop' these days for handmade items & I think you'll find them in short supply , and with premium prices .
I think this is as it should be , but I am still 'old school' in my collecting 'standards' .
I guess dinosaurs still walk the earth ...