Looks like AT to me. Still worth the price of silver but no premium. Premium means the price over face value.
A 1991 ASE in that condition is worth about $25. The toning pattern would be classified by most collectors as AT, or artificially toned, as @fretboard pointed out, thus the toning would not fetch any sort of premium on the market. Most bullion ASE's in that condition are around the same price, and what @Collecting Nut was getting at was he was unsure if the 1991 year was some form of rarity (i.e. low mintage).