Drop-In Iris Machine Screw Size?

The ETC drop-in iris for Source Fours has several tiny flat head machine screws that hold the iris assembly to a guide plate.  Does anyone have the specific size of the machine screw?  It's smaller than a #4 and less than a half-inch in length.

Also, could this information be added to the documentation for the drop-in iris?  Most other products have a very detailed drawing of the product and all its components.

Thank you in advance!

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