What did you think was back again? The tariff exemption?
Yes, the country of origin determines the amount of taxes/duties/tariffs, etc. It's also based on the value that the shipper puts on the commercial invoice prior to exporting the item. If they classify it as a just a transceiver and put the value at $10 that will raise flags with customs. They will assume it's a brand new transceiver. But if they were to put classify it as a transceiver and add a note like "Item sold for parts only. Value for customs purposes only." They can get away with a smaller amount than the actual price of the radio. But they should still be using a reasonable amount for the value of the parts. This applies to new and used items.
If they note that it's being exported to the US for repairs only, customs will be looking for that same item to be re-exported from the US back to wherever it came from. You have a certain amount of time to repair and return it. I deal with this almost daily as part of my job.
Even if they note on the commercial invoice that it's a gift, the correct value is still required to be entered.
I used to work at a place where we had people in from Brazil. Their taxes/tariffs are out of this world. One of the first things they would do when they got here was to head down the road to Best Buy and load up on electronics and video games. They would have to unbox everything and make it looked a little bit used so that they could declare the items as personal effects. They could claim they left Brazil with them and are now just returning with the same items. Several of those guys were making some serious money selling their personal effects upon return to Brazil.