High-quality black-and-white photographs of large old machines and tools

[Toolmaker51]

Or thats just the biggest parting tool I've ever seen!

That observation is not far from reality. The good old day's before CNC...
Expanding the view reveals the tracer pattern, lower left of machinist's feet. The V has an involute-like form, so the stylus is radiused; smaller than where they converge, fillet where they meet parallel sides, and where those meet outer diameter. Many tracers are hydraulic only, depth controlled by crossfeed, first passes
don't create full contour. In mill profiling the cutter is most often ball end. Lathe work then, works likewise, with a radiused tip bit, either case is to scale of pattern and stylus. Roughing was accomplished by changing stylus or cutter size accordingly, as most patterns were 1:1, but ratios work too.
Since parting is still profiling, it's not uncommon to chamfer edges with same cutter before depth gets too far along, using the compound. best results are when [you guessed correctly] parting tool has small corner radii and square face.