Olive web sling used to carry the scope can for the MGZ and MGZ40 sights as well as the can for the 8cm Mortar sight. I'm not sure about other optic cans, but it's likely used for them as well. We have made these using our new, shuttle loomed reproduction 25mm German pattern webbing and we had the aluminum snaps hooks custom made.
They weren't cheap...
Like original Lafette Straps, originals are almost impossible to find.

Which color is correct for X, Y or Z impressions? Gray or olive? Either one. Despite the conventional mis-conception that web gear is "tropical"...it was issued and used on all fronts by the German military. Their webbing came in every shade of olive, tan, gold, slime green, light gray, medium gray and dark gray imaginable. This is a great match for the "typical" olive color seen on most German web gear. The correct one is whichever one floats your little boat best.
I always prefer nice, clear, exact answers. Don't you?