@BhForce it comes with experience and handling antique arms and armour day to day. as it is the same with puratan manuscripts. most sikhs can't tell the difference between a real live blade and a dull showpiece, in regards to weight, edge retention, fit , feel ,shape, you can tell from the quality of the finish , the colour, the thickness of the old and silver work, the designs, polishes etc. etc. most sikhs can't tell the difference between a real antique and a fake aged one from India due to the lack of gyan in that area. Whatever area you study you become proficient in that mode of study.