Early variants. First image is interesting as this shows the two suppressors that were sent out in the early kits, a longer SRD762 variant and then a short one that was labelled as 300BLK Suppressor (Short) on the NSN. Those two suppressors were also part of the first batch of 10 kits purchased by SOCOM in 2018, with the folding/telescoping stock and the Kate Moss thin stock. A later image showed what looked like a SEAL with a Dead Air flashider, presumably for the Sandman. Optic package for those first rifles included the Wilcox BOSS along with the Sig Juliet 4x magnifier. The upper was the refit kit with the SIG stock adapter for use with existing lower receivers. The NSN and part number don’t indicate whether the keymod handguard was ordered, but the MLOK version was in Army testing as of early 2019 and the commercial Rattler with MLOK was announced in 2017, so the keymod variant was likely just for early T&E.
You may remember seeing this early keymod variant in this SCO19 image.
Army testing models from 2019.