Larry,
These Boxes were available in the Fifties for a very short period of time & were designed for Post-War K-Frame Masterpiece's with 6" Barrels & Magna Stocks only!! The body itself is composed of a fibre or sawdust type material & bonded together with resin!! They were formed in a Mold, painted on the Outside Surfaces & Blue Flocking applied to the Interior Surfaces only!! They had problems with the paint flaking as well as some separation problems with the body material itself & were discontinued shortly after they became available!! Yours looks to have survived in excellent condition & as far as I can see is "Completely" Original including the Exterior Paint!! As Daniel stated, they are somewhat Scarce to Rare, but sadly they rarely bring prices you'd expect to see from an item as scarce as these really are!! I own a couple of them myself!! They do make a fine display for Early K-Frame Masterpieces though!! Enjoy!!