You should eventually receive this:
I mailed in the MSI form. I truly believe it won't mean squat if the thing becomes law in Oct. 19'.
It is law now, and it won't mean squat after October '19. The point of the letter was to allow you to continue to possess such devices now.
Got my green card back today. No letter yet.
Second letter - Priority Mail dtd 9/26. BATF/E received 9/27.
Initial letter - RRR dtd 9/17. Green card in my mailbox 10/18.
Neither letter returned by BATF/E as of yet.
My card never came back.
Finally got my letter