From my first hand experience with people who do this for a living in Europe I can tell you that unless you are finding this in a Western country (western europe in this case excluding Greece,Spain and parts of Italy since these european countries have extra tough police who specialize in finding illegal diggers) where there is little interferance by authorities as far as traveling and having detecting equipment goes, you would need major local contacts on your side/payroll otherwise while traveling in your respective non western country should you be found with the tools you used to recover the cache with/or the cache itself not even bribe money will help you and you will spend time in jail , if you are American expect extra harsh treatment, if you dont speak the local language/languages expect super harsh treatment. If you have good local contacts you can avoid the local laws. dig, find, buy and freely remove items through the borders, but expect these contacts to take a major cut of your "treasure" , if you do things solo expect to have a shortened life span, since you would be competeing with the local governments and mafias on their own turf,, they control all illicit/legitamate trades in non western countries, and they dont like competition so expect alot of new partners in your life (many of these people operate on the western end of the chain too, so youre not safe at home either, robbery, murder, threats are common in this business), your next hurdle is bringing it into the US through US customs, thats another story altogether but it is done frequently as we all know, just like the drugs they bring in here. Good luck whatever you do, but expect to have trouble somewhere along the way since what you propose to do is very illegal no matter how old or young the treasure items are! I havent seen one year in europe where the local papers didnt report on "busts" of illegal diggers, smuggled treasure captures at borders. I personally know a few people doing time for detecting!
Rob