Correct, its an old Beuchat VX4 with a basic VS second stage. The VX4 was a balanced piston reg and was bullet proof.
They lasted forever with almost no maintenance, and if its still good I would have no hesitation in diving it.
Its biggest fault was it was a noisy breather as the air flowing over the HP seat set up a resonance on inhalation they could never really get rid of. So if on breathing it you hear a "tinny resonance" almost a squeek - dont worry, its usual.
The VX second stage was just a basic demand valve and as it had access on both sides you could attach the LP hose to use the demand valve on either the left or right side. Quite usual for the day as they often dived demand valve on the left in Europe back then.
Although the VS demand valve breathed very well it was prone to free flows, later it was upgraded with a tensioning kit to eliminate the free flow, (this one does not have it fitted) and the kit is most likely still available as a spare part.
The purge button was unfortunately also an issue, designed to be easily removed, it came in a variety of colors, the idea been to enable you to partially colour code your reg to your gear, sadly this left the button prone to falling off and getting lost along with the purge button spring. Later it was upgraded and the issue sorted out, but to repair that unit you have you would need the upgraded screw on face plate as well as the new purge button / spring assembly.
The VX4 first stage can be overhauled very easily, a few O rings and a HP seat is all thats needed, if you are not able to obtain the genuine Beuchat HP seat the unit will accept the generic HP seat available, and the VS second stage uses a basic flat plate LP seat available anywhere.
These are old units, around mid 90's, but are solid, bullet proof minimalist performers, tune them up and use them, they will be just fine.
Sierra Scuba made good gauges, sadly they stopped around the mid 90's as well, but again if they work, use them, they are good solid products.
If you need workshop schematics and instructions to repair the VX / VS unit PM me, I will be happy to oblige.
---------- Post added May 17th, 2014 at 01:39 PM ----------
I took a look at the Beuchat manual and the best I can tell ( I could be wrong) is your first stage is a VX4 which is appears to be a balanced piston and the second is a VS which is a classic downstream. The manual is from 1999 and the exact photos are not there so either they are newer or more likely older. Maybe from the 80s or so. The manual gives the o-ring specs but I am not sure what you can do for a seat.
Yeah, early to Mid 90's, there were a few models but that particular one is from the early 90's on...
---------- Post added May 17th, 2014 at 01:43 PM ----------
The Beuchat
VS is definitely older. I have one in my parts box...I haven't measured the lp seat, but it's like a Sherwood lp.
You can always flip it
Nothing to write home about...I'd put it on the 'sell' list. Plus parts kits aren't easy to come by (more problematic with the first stage)
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Indeed, the VS was Beuchats first real demand valve from the mid/late 80's and they used it for all the first stage combinations right up to around 2003/4 in various upgraded models.
As Fishpie says it was actually a very good breather and was dead easy to repair, generic parts are available everywhere, you could strip it down and do a complete service in 10 minutes and be back in the water, one seat and a few o-rings, it was that simple.
Indeed Indeed, nice to see a real trusty old Master lift BC in such good condition. Indeed, the pockets flaps were detachable so you could colour combine with your reg etc. I think I may still have one here as well, but not in such good condition. 
