I would like to add here that the early model Swing arm Silveys and especially the red one with the gold anodized arm arm are virtually identical in every way to the original Simington swing arm plain 451. The Simington 451 "B" & "C" have a different motor and additional adjustments on the arm
My "plain Jane" swing arm will do every thing the new ones with the adjustable arms will do if you study how it is made and the inter relationships of all the angles and components.
The original Silvey and Simington swing arm design is the ultimate in simplicity.