I am thinking that was a fairly available padlock in its time. We found one last year exactly like it and it had a us on it. The US camp we were in was 1895. I have seen them plain as well. I consider it a pretty nice find.
I just looked in Arnall's sixth edition and found the brass RR lock on page 259. The price page for that lock says it is a Fraim Slaymaker and was estimated to ahve a value of $25.00 in 1996. I guess no one knows for sure what the RR was for, but it was common in the late 1800's and up until the 1920's to make locks with different designs and markings and then get a design patent to prevent competition from making the same markings. The sub-brand names created by such markings created a dedicated market. Look around and you will see that the name Champion was obviously very popular in those days because you find more examples of it that have survived until today.
The RR lock is also a warded mechanism and the primary reason yu cannot get it to operate is likely that a steel spring was used to do the locking of the bolt. Age and exposure of course have likely destroyed the spring. Hope that helps.
BBE.