Lyman mold designation

[water bug]

I have a Lyman 457132CV mold single cavity. Can someone tell me what the CV means? It casts 525gr to 529gr Boolits with a 20:1 lead alloy used for BPCR Silhouette shooting. I recently cast 50 Boolits and kept them in order . Then I weighed them. The weight slowly crept from 524 to 529 gr. as I cast them with an average 1.4 gr variation in each 10 Boolits. up to the 50 of them . Any idea why the weight gain? I use a LEE melter, and dip the lead. Thanks, WB

[44fanatic]

From the Lyman FAQ site:
Q: What do the numbers and letters on the block halves stand for?
A: Each mould block is stamped of course with the bullet number it will cast. The letters following this number are our reference which tells us exactly which cherry was used. This also tells us its vintage. There are block numbers, each mould will have the same numbers stamped on both halves. This matches up the mould halves in case they are separated.

My guess (new to this) is that the change in weight is due to the change in temp of either and/or the alloy and mold.