I just bought a side by side 12 ga. hammer gun with 30" barrels.

The left side plate says, "Manhattan Arms Co. and the right, "The Interchangeable".

I can find no serial number on either the receiver, barrels or fore-stock. However, there is the number 007 stamped on all three plus the wood of the fore-stock. In addition, the number 12007 is etched between the barrels on the underside. There are various other numbers and symbols stamped under the barrels. One such stamping says, "Choke 18.0/18.0.

"Belgium - Best Rolled Steel" is engraved on the rib and Choke Bore is etched into the left hand barrel. There are what appear to be four "Proof" marks on the breach block of each barrel. The stock has a silver shield inlayed on the butt of the pistol grip and the gun came with a steel butt plate that looks to be original.

The barrels are in perfect condition and all parts lock up tight. But what does "Best Rolled Steel" mean?

Anyone know what I bought myself into?