You have neglected to mention that Max Grey imported a nice brass NKP Berkshire in the late 50s. This was scale 2-rail
US HObbies also imported an NKP Berkshire in the 60s and 70s in brass. I think there were more than one run, maybe 2 or 3. This was similar the MG mentioned above but with much better lost wax castings. this is my favorite of the brass ones and a very good runner with a very well-built mechanism. This was only done in 2 rail also.
Weaver also imported a brass one in both 2 and 3 rail. These came painted. They are nice but since they were also done in 3 rail, the front pilot deck was extend and the pilot pulled forward to compensate for the sharper 3 rail curves. This is a very nice conventional runner worth installing your favorite electronics in in 3 rail.
While the newer diecast has gotten very good, I think (opinion here) that the details are sharper and finer on the handbuilt brass models. I think all the brass stuff is hand assembled in smaller runs.
