On both the E. Remington & Sons and the Remington Arms Co. hammer guns the steel barrels were marketed as "Decarbonized Steel." Now what was the difference between the "Decarbonized Steel" on the Remington Arms Co. Model 1889 hammer guns and the "Remington Steel" barrels on the K- and A-quality hammerless doubles being made at the same time? Here is what Remington Arms Co. had to say about their steel barrels in their 1898 catalog --
1898 Remington Arms Co. catalog page 6.jpg
They don't say anything about the Decarbonized steel on the hammer gun --
1898 Remington Arms Co. catalog page 8.jpeg
but all the pages say "Guaranteed for Nitro Powders."