What you have is the genuine first prototype for a device that Hewlett Packard hoped would make them a fortune, and it did, but not as first intended.
It was originally intended to be the method of choice for mainlining illicit drugs, but it was rather obvious when attached to user's arms, so the proposed technique was to mount it inverted under chairs, and inject into the buttocks very quickly, before users felt the needle.
Unfortunately, plastic disposable syringes offered a slower, longer rush, and the target users were often dying from other unnatural causes.
HP then decided to stick it onto the top of their 5890 GC, and use it as a GC autoinjector. The unit should consist of an HPIB, or HPIL interface card, IB or IL cables, the large control box, and the syringe driver unit. ideally there should also be a 100 place vial holding carousel. HP sold them by the tens, if not hundreds, of thousands, so it has no unique value.
As all of these event occured about 15 or more years ago, the unit is probably no longer supported by Agilent, the entity that HP analytical now exists as. Somebody may buy it for spare parts, but if it's history isn't known, or it isn't complete, the price may be fairly low, but somebody may risk spending a few beans for it.
As it's apparently not complete, even intravenous drug users probably won't be interested either.
Bruce Hamilton