Could be a long winded one but keep it simple.
To be honest i dont think you will find any wear, it isnt a chinese machine with little use.
Check all hand wheels move along their tracks without any loosening or tightening.
Backlash on lead screws and gibs can be easily be taken out, dont worry about that but bare in mind what would it be like if nipped up a little tighter.
More of a concern is bed wear which i dont think i will be able to demo on here in writing. Move carriages up and down and check for any loose or tight spots. May be loose at chuck end and tight at tail stock!
Whilst at it, at strategic points harshly try and lift carriage off the beds and other areas, a must. That will be wear walk away.
No use can still have breakages so check gears engage and will need to rotate the chuck to do so.
Same with power feeds, drop lever in and see if it moves. Parts are available but costly. Another sign of use is the half nut on these 600 group lathes, drop the nut in and try and move carriage back and forth, not a biggy just a sign of wear which can be adjusted out.
You may be able to feel for head stock bearing wear, just feel for any undue notchyness ignoring the straight cut gears meshing.
Personally i wouldnt care if it was mechanically sound, its a tool for doing a job not to look at.