This model Challenger Lift was probably built by VBM (VBM Challenger) sometime in the late 1980's or early 1990's. I believe VBM sold out or filed for bankruptcy in about 1993.
They were very good lifts for their time, but historically, the things to look out for are as follows:
A.) Wear on the inside of the columns (ie. steel shavings on the baseplate or steel on steel contact in the columns themselves). Over many years, the slider blocks which are made of plastic wear out. If they haven't been replaced, the carriages (steel) will wear on the inside of the columns (also steel) and scrape the steel bit by bit off the column.
B.) WORKING arm restraints on the arms. Many of the people using this type of lift have removed the arm restraints completely due to the poor design. (It was state of the art at the time, but has since fallen out of favor due to poor reliability, cost to replace and being a PITA to use.
C.) Rubber pads on the lifting pads. Many users of this lift never bothered to replace the rubber pads after they wore out or ripped off.
D.) Working safeties on the carriages. The older versions of this lift had individual safeties on each column, rather than a single point lock release. The single point lock release was pretty easy to damage and once damaged, was rarely fixed.
Going rate for this kind of lift in our area (Northern IL) is about $1,000.00
Not all parts are still available for this lift, if memory serves. Arm restraints may be available, but will probably cost more than you pay for the lift.