1891 was when USA passed a law that all imported items had to be marked with a country of origin. Because many of the Sheffield knife manufacturers exported their knives to USA, they rapidly complied and marked "England" after "Sheffield".
Your knife has no "England" so someone thought this meant it was made before 1891. I think it is a much more recently made knife and definitely not made by Jos. Rodgers & Sons. Stainless steel was first used for knife blades in 1920's and did not really catch on until after WW II.
This brings up the maxim: "Read the knife, not what the markings happen to say". Sometimes the font or size of the markings can indicate a certain time period, but what they happen to say might not be correct.