I'm about to buy a used La Marzocco GS3 AV, would anyone be so kind to give me some quick pointers of things to look out for to make sure everything is working as it should?

The current owner doesn't know when the machine was built but he was able to provide me with a picture of the serial number.
It says "S/N 0054" and "DATA "0407", if that's of any help to you guys. Does this particular serial number belong to the machines that had certain issues or were part of the "fire sale"? Is there a way to look up the date it was built?

As I understand, the machine has plated brass groups instead of stainless steel ones like in the newer versions.
The guy is asking $3200 for it, would you guys consider it a reasonable prize for an older but otherwise well preserved GS3?

Thanks in advance for any help!

This machine pre-dates the fire sale machines. Their serial numbers were in the 500-700 range.

However, it's a very early model, possibly from the first production run. Given the age, I would make sure there's no leakage from the boiler seals and other fittings. It would be a good idea to replace all the check valves.

Also, there are a number of updates that should be installed, including the new style vacuum breaker valve and at least one additional check valve (I know they added one, but it might be more than one for your machine). I think they changed the steam boiler OPV, but I'm not sure. Probably smart to replace that anyway.

Best to contact your local LM office to see if they can give you a list of updates or any other advice.

I believe there have been a few firmware updates since the machine in question was built. You should ask the owner for the version (displayed when the machine starts up.) I would consult with your local LM office about whether an update is advisable. Note that it's not trivial to update the firmware -- it takes a programming interface, a computer and some expertise, and you have to open the brain box.

Personally, I think $3,200 is a bit steep for an original GS/3. The brass-plated group head doesn't excite me, the updates will cost some money to buy and install (in addition to any other repairs that are needed), and the firmware is probably old. Here in the USA later-model used GS/3s sometimes come up for sale in the $4,500 range.

Here is an incomplete but nevertheless substantial list of changes to the machine with higher S/Ns than your machine: La Marzocco GS/3 MP Review

You won't be able to do the pump noise/vibration reduction mod without replacing the frame, and that would be a massive disassembly and re-assembly job. They added a bushing between the pump and motor, which pushed the pump far enough to the left to hit the left cover. I would guess that the new frame has the motor mounting holes offset to the right to compensate (or maybe it's a wee bit wider...)

If your machine is too loud or vibrates too much, you could try replacing the stainless steel hose that runs from the pump to the mixing valve. They made the hose a little longer in an effort to reduce noise. Some owners thought it helped, but others didn't. None of the other suggested mods really solved the noise and vibration problem.

What I did was outboard the motor and pump. If you're familiar with working with AC electricity, it's not a difficult mode. Basically, you have to go into the brain box, disconnect the AC line that runs to the motor and connect the outboard motor AC line to the same contacts. I added an in-line on/off switch so I could turn off the pump to get line-level pre-infusion.

Rather than trying to remove the stock motor, which requires removing one or both boilers (a tough job), just buy an aftermarket motor. I paid about $165 for mine. The pump is easily removed and transferred to the new motor.

To connect the pump to the GS/3, you'll need a much longer pump outlet tube. La Spaziale's plumb-in hose is perfect for the job: five feet long with compatible fittings.

A few years later, I replaced the pump and outboard motor with a gear pump and a homebrew circuit for pressure profiling. Having the pump/motor already outboarded made that a much easier job.