Khums, Heavy Machines and Licenced Looting in Syria

"Thanks for the bullets"

There is another article about the funding of ISIL militancy through the antiquities market, although the emphasis is shifting from the 'Terrorists (sic) Digging up Sites' model to "Terrorists (sic) getting money from antiquities trade" what is to be noticed is that its the same individuals involved, and drawing on the same information as in earlier accounts. We need some other sources of information. Anthropologists  Amr Al-Azm (Shawnee State University) and Salam al-Kuntar (University of Pennsylvania) are joined by Brian I. Daniels (Penn Cultural Heritage Center at the University of Pennsylvania Museum) for a Sept 2nd 2014 New York Times op-ed called 'ISIS’ Antiquities Sideline'. They base what they say from information received from participants at their training session in southern Turkey, where they "were training Syrian activists and museum staff preservationists to document and protect their country’s cultural heritage":

In extensive conversations with those working and living in areas currently under ISIS control, we learned that ISIS is indeed involved in the illicit antiquities trade, but in a way that is more complex and insidious than we expected. [...] ISIS does not seem to have devoted the manpower of its army to the active work of looting archaeological sites. Rather, its involvement is financial. In general, ISIS permits local inhabitants to dig at these sites in exchange for a percentage of the monetary value of any finds. The group’s rationale for this levy is the Islamic khums tax, according to which Muslims are required to pay a percentage of the value of any goods or treasure recovered from the ground. ISIS claims to be the legitimate recipient of such proceeds. The amount levied for the khums varies by region and the type of object recovered. In ISIS-controlled areas at the periphery of Aleppo Province in Syria, the khums is 20 percent. In the Raqqa region, the levy can reach up to 50 percent or even higher if the finds are from the Islamic period (beginning in the early-to-mid-seventh century) or made of precious metals like gold

This however I think is new: 

The scale of looting varies considerably under this system, and much is left to the discretion of local ISIS leaders. For a few areas, such as the ancient sites along Euphrates, ISIS leaders have encouraged digging by semi-professional field crews. These teams are often from Iraq and are applying and profiting from their experience looting ancient sites there. They operate with a “license” from ISIS, and an ISIS representative is assigned to oversee their work to ensure the proper use of heavy machinery and to verify accurate payment of the khums.

I'm a bit lost by the bit about ensuring "the proper use of heavy machinery" (from a health and safety or archaeological point of view?). Also a few months ago I spent several days closely examining the satellite photos of most of the major tells and sites in Syria (only Google Earth to be precise) but on none of them were traces of looting by mechanical excavator visible, pockmarking by what would be likely to be hand-dug holes, with the spoil heaps scattered around them, no evidence of machine work (what there was were military entrenchments). These were not the latest photos, but I'd be interested to hear where there is satellite evidence of this mechanical digging. Although this was a new angle, the next bit we've heard before: 

In addition to the looting, ISIS seems to be encouraging the clandestine export of archaeological finds, which is primarily centered on the border crossing from Syria into Turkey near Tel Abyad, an ISIS stronghold. There is reason to suspect that ISIS has approved and encourages the transborder antiquities trade. In institutionalizing this system, which provides ISIS with one of its many diversified income streams, ISIS has caused irreparable damage to Syria’s cultural heritage.

What I'd like to hear is how that alleged khums is calculated, is there a middleman who buys the antiquities from the diggers and are the diggers taxed on what he pays them? When the stuff is taken across the border by the middlemen, are they too taxed on their profits? How? Or are the dealers coming across to the ISIS side of the border and the transactions taking place within the so-called "Islamic State"? The problem is, isn't it that neither Syrian activists and museum staff preservationists nor Al-Azm, Al-Kuntar have actually seen these transactions at the border taking place, they are repeating hearsay.