GD&T modifiers |F and |F/C

Do you have datums F & C?

Did someone not know how to generate F-C in the FCF their CAD package or something?

In fact, a number of the call outs look odd in various ways so I'm wondering if someone that didn't know GD&T &/or the relevant CAD system did the drawing.

Yes to datum C but no to datum F. It is drawn to ISO standards by a German-language company. I believe the rounded rectangles surrounding the dimensions are related to key characteristics that require statistical verification.

The obround frames appear as infamous SolidWorks "critical dimension" symbols.

The numbers on the very right (4, 6) are probably references to QC sheet / inspection report.

Given the difference in accuracy between DIA 85 and DIA 80.5 (M6 vs. H6) one may speculate F and F/C means something like "Forged" / "Forged/Cut" but that just my imagination.

The appropriate ISO standard for castings is ISO 8062 (old 1994 or new 2008 parts 1, 2, 3). Something tells me you won't find F / F/C in there.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

OK, does the F stand for Fine or similar, perhaps to ISO2768 or similar?

Found something: letters B thru K are used to indicate required machining allowance grade, BUT they should be used in general note and not the individual dimensions.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future