Any chance it says C HCH GBF ?
C -- would be for a level line of C size,
HCH -- would be for a double taper, I would expect that a 6 or 7 Wt DT ought to do the trick.
There are many charts that will allow you to convert from the old silk letter sizes ( based on diameter ) to the modern number sizes ( based on weight). There are disagreements from chart to chart, as you might expect in any attempt to convert a diameter system to a weight system. Also silk lines have a different casting feel than plastic so personal preference and casting style will make a difference in your choice.
AgMD