Iran Revenue Overprint Chancellerie

Dear,

I'm looking for an estimation of the following stamp.

Specs:
2 Kr
Postes Persanes
Overprint: Chancellerie

Would love to know the history of this stamp, can't find much of this one to be fair.

Iran 1911 Customs Revenue, I have no idea the value.

*BUMP*
I believe this was not used for customs fees on goods because there are the 2kr blue stamps issued the same year (1910 according to the Forbin catalog) with various types of DOUANES overprints used for that.

Chancellerie is the Ministry of Foreign Affairs. The implication is that is was used for passport/entry fees for visitors from outside the country, for one, but that is just a guess. So that kind of customs fee.

I have a couple examples of this and have seen others, so it is not rare. Based on the Forbin price (1915) I would take a stab at it being worth a couple of dollars. There is The Revenue Stamps of Iran by Baharaeen and Brooks that might be available via interlibrary loan from the APRL.