619 is probably not a Jet designation- as far as I know, the smallest
lathe they have ever offered was an 8" x 18" which was styled on a
unimat- it included a small milling/drilling head. This lathe was
called a "818", as all jet lathes have been labelled by swingxlength.
IE 1024, 1236, 1660, are common Jet lathe names. Their smallest common
lathe is the 9x20 size.
Could be its a totally different size of Jet lathe, or it could be not
a lathe at all- hard to tell without more info.
The little Jet lathes, the 9x20's are similar to the other 9x20 lathes
out there- but usually Jet is more expensive. they sell new for about
$750 to $1000, depending on the model.
Resale value depends a lot on where you are- in urban areas of the west
coast, it could be 75% of new. In rural areas of the northeast, it
could be as low as 10% of new. Depends on supply and demand, local
attitudes,and condition.
If it is a good shape 9x20, and it has some tooling and a stand, resale
is likely to be at least $500, but again, your location could be
totally different.