I don't know if I can add much, you have found that Mr MacFarland was a gunsmith and author on the subject.
The Jaeger double lever scope mount is a derivative of the Griffin & Howe side mount, although not interchangeable. Side mounts were popular at one time because they were quick detachable and left the top of the gun completely bare for use of iron sights. This was more important when scopes were less rugged and less well sealed than now. Also suitable for an elephant gun used at short range.
I cannot tell if that is a plain trigger shoe on the trigger (I would not want one on a hunting rifle.) or possibly a Canjar single set which would be used for long careful shots.
I don't know why he finished the bottom metal white, a styling element I have not seen on other nice rifles.