I my self used to turn stuff in; I hunt all over Europe and each country has their own set of laws on this stuff. In Italy I still turn stuff in because they are the most honest I have found. In Germany I stopped after two years because I would turn it in, file the paperwork and have record set in place. When I would go back, they would say that the owner picked it up.
Then I found out the finders law in Germany about 2 years later and I returned and asked for public records to file my claim to each find. At first they attempted to treat me like crap for being an American (typical) and asking for such, then I showed them the law and they attempted to tell me it did not apply, then I showed them my Interpol Credentials and called in the Federal Police and Assistant State Attorney whom I set up all this with prior to that visit.
They really tried their best then to back up and speak to me differently; all it got that entire office was search warrants for all their homes, vehicles and office; they where charged with government fraud and a few others; really just a big show and arm flex to oust the tard(s) who where taking the stuff.
In the end the truth came out; I never once figured I would see anything from it, I just wanted to ensure that whom ever was taking the stuff had a good time in their new cell.
In Spain there is no point in taking it in; they will tell you right to your face it does no good and they are not doing the paperwork and to just take it out of there.
Italy is good though, you get it back plus paperwork for the tax man when you sell.
The only reason I ever started turning it in here in Europe is because I only hunt for profit but do not wish to register a business as those taxes are much higher. I sell directly to federal or state refinery's valuable metals and clear on average about 200K a year. The thing is if I did not have all the paperwork that comes with the process then local Tax agency's and the US would really question as to where that extra income is coming from with a man who is retired US Army and currently working for Interpol; the numbers would not add up for the tax folks, then they want explanation which cost more money and can lead to a very long year.
This way I flood the 4 countries I pay taxes in with paperwork through my tax attorney and I have never had any issue.
My son however has had issues in Germany; he holds both US and German citizenship. When he turn 12 about 11 months ago my wife and both felt he was now old enough to run his own hunts, document, catalog and sell his finds. He made his first sale in November of 2015 which came to a little more than 7000 grams of silver and 1000 grams of gold.
He sold directly to the federal refinery for 3% under spot. He kept his records in order and clean but when that transfer hit his account the tax man stepped in. First claiming that I was hiding money under his name, but he showed the paperwork from the refinery and that cleared that up, but then the tax man said that my son is Too Young To Pay Taxes in Germany. Yeah no sh*t; and then said if he is too young to pay taxes in Germany then he can not have more than 9,000 Euro in his name by the end of the year.
We just laughed at the tax man, even the 2 cops that showed up to our house as his escort where making faces like that is some dumb sh*t to say.
In February my agency had already gone through the proper channels in securing statements from the 2 Officers who where here and we reached out to the State Attorneys office and had a sit down with the tax mans boss from that local office. It was basically explained to him that yes my son is too young to pay taxes but that Germany does not have any laws at all as to how much money someone under age can have. My agency then explained that if any further undue investigation was to proceed that my Agency and the US would take this very serious and move forward with it.
That poor tax mans boos sat in that 1 hour meeting just listening and not saying word, when it was over he told us that he had no idea that someone from his office would try to imply such things after the legalities where settled. I felt sorry for the guy because his worker let him walk into that meeting blind, no idea what happened to the worker after that but my son sure thought he was walking on water with his money until we explained to him that when he does become of age to pay taxes that his first year will be paperwork hell and he can sure bet that he will pay taxes on his interest and whatever he has sold that year in both countries.
So if your hunting for profit, then turning it in is a good thing if you selling a large enough amount to pay taxes on, just have to make sure you get that paperwork.
It is always better to provide the tax agencies with more information than less or it will cost you more in the end when it catches up to you.