Anyone here familiar with the old steel Weaver k2, k3 etc out of El Paso?

I picked one up and was surprised to find I could remove the eyepiece entirely, exposing the internals.

Is that how they were made back then?

Yes, you can take the ocular end off the old Weavers. As far as I know, they were not nitrogen filled at the factory. You can send them to Iron Sight, Inc. in Tulsa, OK for overhaul and reticle changes, if you desire.