I have a very strong feeling thoes pics were, pre-installation - meaning it had not yet been sealed. I seal most my blocks with RTV Silicon (used to solder them, but no more). I usually put a thin layer of RTV Silicon (room temp. vulcanizing ... btw) about 2mm in from the edge of the copper... screw the top on slowly until the layer of silicon reaches the edge of the copper all the way around, remove the excess silicon (that came out past the copper. Then wait until the silicon dries, your particular tube will give you an idea of how long. Then tighten the blockfully and pressure test it - should be A-OK. But like I said it doesn't look like Puzzdre has gotten that far, just taking pics for us ato gawk at
