Maybe we're dealing with a different idea of "full-length" here. The description otherwise pretty-much matches a DCM-style conversion. Carbine stock and band (no swivels), M1905 front sight (1" band around muzzle), plus aftermarket receiver sight replacing cutoff, minus handguard and issue rear sight.

Lacking photos, my question is "How far from the muzzle is the tip of the forearm and is there a band spring (spring retainer for the barrel band) present?"