Well, it seems like there is little solid information on Iranian ammunition production. Ken Elks covered Iran in his book "Ammunition with Arabic Markings," even though the cartridges' markings are normally in Farsi, not Arabic. The alphabet is pretty much the same I am told. There are some number differences, primarily with the digits 4, 5 and 6.
Regarding the ammunition factory at Teheran, the factory probably opened just before or during WWII. Most of the 7.9 x 57mm ammo made earlier has been identified as contracts by companies like Deutsche Waffen- und Munitionsfabriken A.-G., or Fabrique Nationale d'Armes de Guerre, of Belgium. Dating is tricky, as they used a calender based on the year A.D. 582 until about 1925, when they switched to one base on A.D. 621, In 1926, D.W.M. made a contract run of 9mm Parabellum and of 9mm Kurz for Iran. I have these cartridges and their boxes in my collection. I also have two different years for .45 A.C.P. but no box labels, and I have not yet had the headstamps interpreted. Unfortunately, I lost my Iranian neighbor, who moved away.
As late as 1950, some Iranian ammunition was still made on contract. There was a Belgian contract for 7.9 x 57mm in that year.
According to "Global Security.Org." a factory making small arms and ammunition was established in 1939 at Parchin, and has been in operation since right before WWII. I do not know how to identify any small arms ammunition made by this establishment, however, if indeed, the information is correct.
Today, Iran operates ammunition production under the name of Ammunition Industries Group (AMIG) of the Iranian Defense Industries Organization (IDO). They make, among other things, 5.56 x 45mm, 9 x 19mm, .38, .40 (presumably .40 S&W), .45, 7.62 x 51, 7.62 x 39, 7.62 x 54R and 12.7mm (I don't know if that is the Russian Round or the American .50BMG - it is not stated in my source - "Small Arms Review, Vol. 4 No. 11, August 2001, page 92).
The rifle guys are lucky - some of the Iranian ammo shows up for collectors in Kashnikov and NATO. Don't know about the others. However, the only Iranian-connected 9mm Para I have is the DWM contract of the 1930s, and the same 9mm Kurz and a couple of .45s (one a fired case). I have never seen or even heard of a .40 pistol round with Iranian headstamp showing up.
This doesn't answer much of anything, but it is all I have to offer unless I simply copied verbatim Ken Elks section on Iran. Some of that has me confused, to be honest, as he doesn't really seem to know the meaning of a lot of the headstamp entries, nor do I. I hope it is of some little help and interest, anyway.
One other caution. Many of the "Iranian" 7.9 x 57 Mauser special purpose loads - blanks, dummies, etc., are not of Iranian manufacture or use. they were made on fired or left-over cases by the German firm of Huck after WWII.