Hi, Don,
Its the 'proven to be in good condition' aspect of your question which becomes a bit of a challenge.
If I may hazard a guess, it would be that you could put more in the value of your time into getting it into 'proven good condition' than you could ever recover in selling the unit. Having the usual sort of 'low-wage workers' just 'pretty it up' could do more harm than good.
Since it appears to have been in storage long enough to get a bit of rust on the ways, 'proven good condition' would mean having it apart, de-rusting the ways, and inspecting the alignments on re-assembly. It could be pretty badly hurt by 'just getting it running'.
That one has the look of an early to mid 1950's machine, and is a known good make, so, for the right person, its well worth the amount of working time needed to restore it. (actually, thats a 'maybe'.......as the state of wear of the cross-rail would be an unknown til its cleaned up and properly inspected......from 'general appearances', tho, I'd call that one a 'good risk'.....unless it has damage not visible in the photo.)
Knowing provenance would help, possibly. If it was, for example, known to have come from the machine shop on board a Naval vessel, or had come from the toolroom dept of a plant, as was little used, that would help a prospective purchaser to think it might have been well cared for, and not used abusively.
Whatever its provenance, tho, it has to come apart for proper cleaning of the ways and oiling system before it is used.
Granted, this is only a guess, but I'd say that your best option is to offer it 'as is', to a machine hobbyist who doesn't have to value the time invested in having it down, and checking it out. That one is a desirable machine of its type, for the person who has the spare time to 'give it some love'......and thats quite a few hours of serious 'loving'...... : )
If I may offer a suggestion, it would be this........offer it in the 'antique machinery' section here, for 'best offer by 'X' date. Instead of doing 'sealed bid' by 'X' date, as in the DRMO sales, you could post 'best offer so far'.....and set a 'minimum bid'........if it was mine, and I knew the motor would run, and it passed a reasonable visual inspection of the gearing and general state of condition (no bad abuse marks), I'd try starting at $1000 'as is'.
If I was a potential purchaser, meaning that I had the need for that capability, and was willing to invest the many hours of time in having the machine down and going through it, I'd value it at that level.
cheers
Carla