This is probably no help but the 1956 catalog shows the standard rear sight was a Redfield 75RT with the front being a Redfield Globe #68. I had direct contact with a LOT of these nice rifles issued by the DCM to Junior Rifle Clubs. at least half had Lyman Sights on them and have little doubt they were probably an "option" when your rifle was produced. It has been a good long while but believe the factory drilled holes for the receiver sight were such that they would allow either Lyman or Redfield sights to be used, Vaver sights were also popular for the 513T. If you want the opinion of an experienced small bore rifle shot, I will tell you that we thought a whole lot more of Redfield & Vaver sights than Lyman for Target use.
I wouldn't worry about it, its still a nice sight and will do the job.
Jim Peterson
Charlotte, NC
Original Lyman Sights on a 513T
Re: Original Lyman Sights on a 513T
Jim Peterson