Rifle, U.S. M1, .30 Caliber blast deflector...

Received my copy of the Rock Island Auction catalog and seemed to be immediately drawn to lot 1535.  This is an M1 Rifle (Garand) with a unique blast deflector reportedly locally fabricated and used only in Alaska.  This is a gas-trap rifle.  A photo of the blast deflector is shown below.  Bruce Canfield's new book doesn't seem to mention it but it is possible I've overlooked that somehow.  Very interesting to me.  It would seem that it would have to be removed for operator cleaning.  The catalog copy says that only 3 are known to exist.  I've never seen or heard of one before.  Accordingly, this rifle's estimate is between $30,000 and $50,000!