What your pictures show is, indeed, a hand built lathe. The person who built the lathe was most likely a machinist or toolmaker. The lathe looks like what is called (in slang) a "government job". Amongst people who worked in machine shops and similar industries, doing a job for home or getting materials from work for personal jobs was known as a 'government job'. The lathe looks like a government job. Something the builder could machine parts of using stock that was at hand in the shop where he worked. The use of socket-head screws and plenty of steel plate milled to dimensions also speaks of a government job. The knob to t he left of the headstock and set up high (which looks like a knob from a combination lock) apparently is part of a mechanism to use the lathe spindle for 'indexing' (dividing a circle into equal parts such as for cutting gear teeth, splines, or other mechanism parts).
The fact the builder assembled the lathe using screws also speaks of a government job. Using screws to pull the various parts together would let a person machine the parts at work then take them home to assemble them. Truth be known, it would have been a lot easier to have built the various sections of the lathe using welded fabrication and then machine the completed part. It was more labor intensive to have to make all those connections using screws (and probably dowel pins) rather than welding. My guess is the builder worked in a machine shop or toolroom without access to welding equipment, or may have been taking the lathe home "one piece at a time" with what fit in a lunch pail or inside one's shirt or coat to get out the gate un-noticed.
At the same time, there is a lot of machine work that went into building this lathe. Possibly, the builder had the OK from management to work on the lathe on his own time in their shop, still as a government job.
The builder went to a lot of trouble to design and build this lathe. I kind of doubt that cash was so tight that he could not afford to buy a small bench lathe such as a South Bend, Logan, or Atlas (sorry about using the "A" name). It may have been the challenge of building a lathe, or maybe the builder had some definite ideas in mind such as the indexing feature on the headstock spindle.
I'd suggest you contact Tony Griffiths who runs the "Machine Tool Archive" website. Tony posts articles about 'unknown lathes' built by persons unknown and of interesting design. A writeup of this lathe would be the kind of thing Tony Griffiths would add to his website.