I lost all mine in a boating accident while fishing the canyons.It's not 2013, it's Jan 13th 2023. (Original post edited for clarity now)
The BATFE is requiring proof that you owned the (now) "SBR" in it's current configuration with the (now) naughty pistol brace if you want a free tax stamp in accordance with ATF Final Rule 2021R-08F. Otherwise you have to go through the "regular" eForm 1 process and pay your $200.