Hi,
Welcome to the forum. I am no expert but from what I have read ( mostly from ads) it usually weighs about 30 gms plus. The c cases, it seems to me, tend to be heavier than other styles.
From what I have seen they were a 70’s style ( came out in the 60s) and commonly came with “bricks“ style bracelets.
There are entire threads dedicated to c cases in the forum and experts concentrating their collections on them. They will be able to give more accurate information. Also the information to date them exactly is inside and an opened up photo will help.
lovely watch and wear in good health.