In the meantime, I did find some markings on the upper side of the barrel under the existing Weaver rail and scope mount:

C.R.HART
22 L.R.

For those who might be unfamiliar, Hart Rifle Barrels was founded by Charles and Clyde Hart in the 1950s, and the company remains a leading barrel maker. This, of course, helps explain the accuracy of the gun.

Enjoy!
Dave