I never got scientific. In my case, I would haunt gold and silver shops and pawn shops for years. Those guys know what they are doing, and I never found something priced wrong. When I started looking at ancient collectables,  I would find dealers where the numismatic value would almost be at the price of bullion. This happens, or used to happen, sometimes with St Gaudens double eagles priced the same as a bullion eagle. I also recalled that happening with gold 40 franc Napoleons. 

siggy47

there are lots of coins and medals minted in the modern period that, with a little patience and practice, can be acquired for below spot. 

for ancient coins it can happen too, but it's much less common 

plunda

history

A piece of history and a store of value.

> I too discovered ancient coins around 10 or 15 years ago. I also started by finding below market gold and silver. 

You mean you... found physical ancient coins and their silver weight is worth more than the market value for these coins? Really? That seems like a very odd market inefficiency.

Have you used a metal spectroscopy device on it?