The 5″ with which I was in contact was in a basement and used to produce small, parts for war work.
(Sorry, have had no feedback as to the Serial no.)
It a gearbox type, with power feeds for both Saddle and Cross Slide.
By suitable choice of changewheels, and gearbox settings, it was possible to set up a fine feed.
Since there was a choice between the 4 way toolpost, or a Top Slide,(You could have one or the other) I made a rather thin 4 way toolpost for the Top Slide.
It also has a taper Turning Attachment, although my friend, and now his son, have never used it.
It is a long time since I saw it, but think that there may have been a collet attachment and collets, as well.
I’ll try to remember to ask again about the serial number
Howard