headstock question

[trainguytom]

Need a little help from the brain trust on this.
I just bought a shopsmith where the main machine is an old greenie, but the headstock is newer. I bought it for the headstock which runs really sweet. The rest of it will, after a ton of cleanup, be made into a shorty power station.
Here's what I'm wondering about, because this is the first time I've seen it. The serial number label says:
Headstock (Serv)
Model #516903
Serial #060592
I know the serial # is the production date, but I'm wondering what
headstock (serv) denotes. Was it factory serviced and then had that label applied, or does that mean that the owner just bought a new headstock for his greenie?
Also, I'm not familiar with the notation of model #516903. My other machines don't list a model #. Maybe that means the headstock was a separate purchase?
Any info would be appreciated.

[Beave2012]

Also, I'm not familiar with the notation of model #516903. My other machines don't list a model #. Maybe that means the headstock was a separate purchase?

516903 - Headstock 60hz 120v Domestic
http://www.shopsmith.com/ownersite/item ... tem=516903 (Product Catalog)
This item is a service or replacement part. If you have any questions about this item, please contact our Technical Support line prior to ordering. The number to call is 1-800-543-7586. Thank you!

So the main system was a 1953-1960 greenie and in June of 1992 a new headstock was purchased to replace the old one for whatever reason. Now the only question would be if its a 500 or a 510 since its almost a frankensmith. Either way the headstock is the most important since the rest of the machine is built like a tank.

[trainguytom]

All the parts except the headstock are greenie based. Altho it's built like a tank, rust on the steel & oxidation on the aluminum parts make it a pretty rough machine. Oh well, I did get a biscuit joiner, drill chuck, sanding disc and lathe centers, so I think it was $150 well spent. The date on the headstock should mean a 2 bearing quill.