Lets figure this out.
Do you know the person who owns this? Can we get more pictures? There is a contraction on the back which was not photographed.
It is constructed from a moped although I do not see a gas tank. I do see moped spocket and back wheel.
Looks manufactured rather than cobbled together in a workshop.
Does not seem to be a general purpose detector because the coil is fixed to ride on the ground which would not work around obsticles. Coil has runners which, at best, would allow it to follow contour of ground. Also, stock front moped tires, which would ride on sand pretty well, have been replaced by flat, more narrow tires which would sink in the sand but would work best on a concrete surface. The coil swings up out of the way for transport or non-use position.
I see headphones (front and back), junk bucket, optional handheld detector wand (appears to be a folding type), headphones, protected control box, battery or tool box, a flourescent orange gizmo on a shaft laying on the botton tray, 2 sand scoops, 2 water bottles in holders.
The optional hand help detector appears to have a large coil of wire attached for distant searching.
Below the support fram, right behing the handlebar downtube is a white pvc tube (a possible digger holder?).
Partially hidden by the junk bucket is a red, adjustible length shaft.