ORIGINAL: Pydpiper

I was at my Father in Laws today to show him something.. And I stumbled across an old crossbow in his basement.. There are a couple small issues with it, there is no string, and the scope mount is broken..
Does anyone know anything of this thing, it is a "Crisbow MK III"
Looks like a pretty decent old crossbow.. If we can get this thing back up to specs I just may have a new hunting buddy..

So, How does one go about determining string length? It is a carved tip (feels like steel, but I don't know..)
Where would I start looking for parts, that scope mount needs replacing.