A good flashlight and some patience is what it is going to take. If it has been painted over, and you get lucky, you might be able to remove the paint on the old sticker and find it. If not, you are Sh*t Out of Luck, up the river without a paddle, or blowing in the wind. Take your choice. The sweetness of buying a grey market tractor is soured by the lack of support you will get from the domestic dealers in the US.
A friend of mine learned that when he purchased a grey-market Mercedes. The only place he could get parts for it was in Germany, and it took months to get them imported to the US. He had to find someone in Germany who was willing to buy them for him and then ship them. More than once people would take his money and then he wouldn't ever hear from them again.