ww2 sling ?

[lboos]

I forgot where I got these two pic. but the caption said it was taken during WW-2 on some island in the Pacific.
By their helmet cover's I would guess Jarheads ?
I'm still confused about the D tip slings being used in WW-2 and used by the Marines, if true it was the first piece of equip. the Marines got that was not 1'st worn out by the Army, I've always heard the C tip slings was the 1st ones used on the M1 carbine and that "maybe" some D tip's came near the end......Stilled confused.