The “C” series was a Browning only serial number flavor.
I have a 75Cxxxxx Alloy frame, which was made only for the European market. It was mated with an '81 FN slide when I acquired it... but was an import. As an Alloy Frame, its original slide was likely marked FN
and replaced by an LE armorer. I believe there were no Browning marked Alloy Frame pistols.
* Looking through various reference books, I find little information re the C-series, other than it was a new inventory management system and there were changes to production in polishing, applying serial numbers with a different location/stamping technique and so on. They were produced alongside the T-series pistols for a number of years. I suspect, due to the info on the Browning web site re serial numbers, that Browning only imported C-series pistols at some point.
It seems no one has written a complete history of BHP serial numbers. I imagine this would be a time consuming project.