How many stamps would be needed?

If 1 has a pistol and want to put a stock on it then 1 needs a SBR stamp since it is now a short barreled rifle. but then when 1 wants to take the stock off and mount it (pistol) underneath an AR it now is a AOW and that need also a stamp.

But then 1 wants to mount a vertical hand-guard on the pistol either off or on the rifle does 1 need another stamp?
So how many stamps would be needed to cover all 3 scenarios?

Thank's:th_shrug: