As LaOtto explained, H&R doesn't make a stainless frame except for the 45-70 and 444 Ultra Hunters which were first available in 2008, it's always possible some wholesaler special ordered the 44/20ga combo with stainless frame if it was made in 2008 or 2009, but if if was made before last year, it will have a nickel plated frame, possibly a stainless barrel, they've made stainless rifle barrels for many years, shotgun barrels were nickel plated tho. Let us know whatcha learn. Same on the SB1 vs SB2, SB1 weren't available until 2008, if it is an SB1, it will be marked on the right side of the frame that the only rifle barrel that can be used on it is the one that came with it.......if it's a factory issued firearm.

Tim