Once I saw in a numismatic shop a lot of mixed Swiss coins for just 5€. I asked the seller if I could open it and buy only the dates I needed (I don't collect Swiss coins by date but I saw some silver through the plastic bag ). Initially he wanted me to buy the whole lot but then he allowed me to open it. I picked 2 silver 1-franc (including a 1913), 3 silver half-franc and a non-silver 5 francs. He said: "6 coins, 0,20€ each, 1,20€ in total". I kept 1 franc and 1/2 franc for my collection, sold the other 3 silver coins on E-Bay for 5€ and exchanged the 5fr coin with a friend that was departing to Switzerland (4€)! I also picked up 6 US silver quarters, 3 US silver dimes (including a 1941 Mercury), 3 Canadian silver 10 cents (including a 1943 King George), a silver Canadian 25 cents, 2 50% silver British one shilling and almost a dozen of old Asian and African silver coins, all from mixed bags of worthless world coins of few cents each. Some I kept, other I sold. I was exchanging old Italian coins with another collector. I offered a 1961 commemorative of the unification 500 lire in exchange of a 1949 2 lire. He told me it wasn't fair because my coin was silver and his was aluminium. I replied there was no problem, I just needed that coin. Well, my silver coin was only worth melt (7€ back then) and his aluminium coin (rare date and high grade) around 30€! And I found some pre-unification (late 1700s - early 1800s) Italian coins in mixed lots for 50 cents each. In a lot of old Italian coins I inherited from my grandparents there was also the ultra-rare 1946 1 lira (100,000 pieces minted, worth 100€ even circulated). Have you some similar stories to tell?
Mine is quite quite different, but when I was getting cases of pennies from the bank, to sort copper I found a flattened silver dime in one of the rolls. That was exciting!
Mine happend recently and I posted about it... I bought a 1854 type II princess head $1.00 raw for $139.00 and got it back yesterday graded MS62 from PCGS and sold it today for $3,200.00