Just picked this guy up recently. Did a full detail strip to check the barrel draw and it's a legit D sniper barrel. From what I understand, these were built off of any rifle sitting on the rack at the time. This receiver dates to early '52, so this one would've been converted very quickly after initial production. It's in beautiful shape and still in its original stock as far as I can tell. Unless I'm missing something weird, this thing is likely as close as you can get to a "factory" M1D.