Among the differences is the valve:
These guns are made in two factories / places, one puts orange o-rings into the valves and glues
the valves shut (hard to open again) the other puts green o-rings into the valves and uses
heavy duty loctite to reseal them, these open easily. In fact, time and oil have loosened them,
not often, but I’ve come across two or three that have managed to do this. Both had green o-rings
and the usual double ring grooves in the valve pin near where it enters the valve body are also
not present on these, also they bear no part numbers….. the orange o-ringed valves that
also have the double ring grooves always have a serial number stamped on them.
If yours is the “green” type, you might be in luck and can just reseal and replace the end cap.
I love the green ones because they are easier to open and they are usually a lot smoother
working and better made than the others.
Here's some pics so you can all see what I'm talking about.
Note the o-ring colors and the green one has a steel puncture pin while the other has a stainless
steel pin.
Here you can see the double ring grooves and the part number on the orange one.
.... also note that I have resealed the green one, it has a bit of white sealer showing at the cap 
There are some other subtle differences in the guns... nothing major though.
The 850 Store
