Hardy rod serial numbers suffix C

[Godfroy]

Does anyone know what the suffix "C" means after a Hardy serial number please?

I have a couple of examples in my collection.

In the first photo: On the left an 8' Hardy Hollolight, #5, H37935 (1961) on the right a 7'6" Hardy Hollolight #4, H52040C (1963)

In the second photo: On the left a JJH Triumph, H18431 (1958) on the right a 9' Hollokona Phantom, H42380C (1961)