Thats what I thought was cool about it.Just lucky I guess. Bought arm at amazon. Stem of arm is 10/32 or 5mm same as nuts in headstock. You are able to fold arm out of the way or fold it forward to measure your carriage travel. Most indicator bases were at least 1/4x20 or larger from what I remember
Maple ferrules were on ob1&2 After then came classics. One SBE i bought an ob shaft. The following year I went back to the ob booth and told Royce about some micro splinters in the laminations. He gave me another shaft and told me to keep the old one