Thank you sir for the info that the locking screw is standard on Ruger #1 sights.
What is unusual is that the rear sight locking screw is not listed on the parts list in the Ruger #1 instruction manual I was provided nor is in on the copy provided on the Ruger website. I hope I never loose mine!
I did receive the express rear sight blade from the M77 Ruger Hawkeye African model and it fits my 450/400 NE 3" Ruger #1 just fine.
Thanks again!