Yes, when you get the AP document in the mail the lower right box is empty.
When you use it for the first time to enter the US, the officer in the port of entry will stamp it. He/she should give the stamped original back to you.
If he doesn't, you should politely ask for it - they may forget.
It will save you time in future entries. You or your lawyer should save one original in a safe place.
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