I recently found an early Lyman SA to add to my sight collection. Although similar to some of their other sights it is not just another version re-stamped SA. The base may have used the Marlin E blank with the machining for the spring done on the opposite side - the spring cannot just be turned around in the base and all I have seen with this type spring mount with it on the right side. The base also has a slight curve, which makes sense, but that must have been done after machining because only the thin part of the base is bent, so it's also possible that was not done at the factory.
It's closest to the Marlin E but is shorter and with the sight being possitioned toward the rear of the base it would also sit lower.
Last edited by GeneB; 07/27/15. Reason: added another photo