Very Large Stainless Steel Carrier w/ Leather Shoulder Strap - A Mystery!

On occasion we run across a piece we think is very interesting, but have no idea what its original purpose was. This is one of those. Made entirely of heavy gauge stainless steel it is equipped with a leather shoulder strap for transport. Doesn't appear to have been mass produced. No maker marks. Latches work great. Measures 53" long x 4,25 H x 3.25W. Any guesses?

A NOTE ABOUT SHIPPING. As there is no carton made to fit this, we will heavily bubble wrap and shrink wrap it for delivery. No worries, we've done it for odd size items many times.