A Tale of Two Blocks

We've been using 1/2" genoa sheets since we bought Winsome in March of 2011, and have used that line in what we understood to be original equipment genoa lead blocks.  Note the obliterated sheave and the vastly larger size of the block on the left.  The new block (left) is the replacement, and is advertised to accommodate a maximum line diameter of 1/2".  Hmm...