I avoid customs as those guys are crazy. I used to work for a company that did business across the Canadian border. I drive the truck and one day the customs officials confiscated not only the load I was carrying but the entire truck. They claimed that my paperwork was incorrect. In their opinion I was carrying calendars. In reality all I had was pallets for two months of the year. The sheets only had the name of the month and the days of the month on the sheet. They were not trimmed the size and names and addresses of the company logos were not printed on the pages. But in the eyes of the customs officials they were full calendars, ready to be sold at full retail. It took them 3 weeks to determine the paperwork and customs invoices were correct.
Had on scary incident with US Customs once coming back from Thailand. I had bought quite a few early Thai pieces, (odd and curious money). They flag my backback, asked me questions, etc. I got to keep them however.
Try to keep international purchases under $2500. If it hits $2500 or more customs will hold your stuff until you complete form 5106 and pay their "extortion" I mean customs fee. I haven't had any issues yet, but I have only purchased coins. I'm curious to see how artifacts would be processed.
I have had many coins held at customs over the years while they requested paperwork from me and/or the seller to document their legality. I don't know exactly how many times, but maybe a dozen? There was only one time when I did not end up receiving the coins in the end. And that was because the seller literally admitted they were illegally looted. I don't know who ended up with those coins, but the seller refunded me. All the rest were delivered to me after providing documents & attestations. Maybe half of those in recent years, the other half more like 10-15 years ago. (I don't remember when US Customs first began regularly holding coin. I only found out that was possible when it first happened to me.) In recent years I've tried to be stricter about buying coins for which I can make a good faith argument for their legality. But I didn't always do that prior to about 2013. There was one other occasion about 15 or maybe 20 years ago, something slightly different, an actual theft in transit by someone at or around NYC Customs or USPS. They took about 300-350 of the coins from a group lots of 1,000 uncleaned coins. At the time, there were a bunch of other reported thefts around that point of entry. (But if you look at the IAPN's numismatic crimes website, there are still occasionally outright thefts in shipping.)
Just adding to what Curtis stated above. Make sure you have or can obtain documents from the auction house / seller for all international coin purchases to make sure they are legal to import. You can get more information at ACCG's website: https://accguild.org/Ancient-Coin-I...ricted coins can only,least 10 years prior to Save all you receipts and invoices.
US Customs is not only difficult but it is corrupt - I found that out representing someone accused of smuggling - although he was exonerated, we were told that since the government had spent so much money on the prosecution he had to plead guilty to something even if he wasn’t guilty of anything - in this case he had to plead guilty to a phony minor tax charge. But that wasn’t all - There was a search of his apartment and many items of value taken which had nothing to do with the case. Some were returned but not all even though we had photographs taken by the government of what was taken. I sent letter after letter but we were basically told that too bad your client isn’t getting anything else back. I later discovered that such property thefts were common in seizure cases. I was very much shocked to find out that entities in the federal government were corrupt - I always believed that it didn’t exist at that level - that this was something that only happened in poor countries rules by tyrannies. It was quite an eye opener to find it happening in the US of A and that we were no different than anywhere else. It still bothers me although given recent events it is not surprising.