In this photo we can see the cone or plug and the taper is evident. The valve body has a corresponding taper in it and the two are lap fit or ground to fit and mate nearly perfectly.
The beautiful thing about these robust bronze seacocks is they are made from the same material, all 85-5-5-5 bronze. Eightyfive-three-five bronze is made up of; 85% Copper, 5% Tin, 5% Lead (for machining ease) and 5% Zinc. It is one of the most corrosion and dezincification resistant forms of bronze used in the marine industry.
In contrast most propellers & Prop struts are made of a Manganese Bronze which is anywhere between 26% & 40% Zinc. Which of these "bronze" materials do you think will last longer in the marine environment? There are no dissimilar materials in most tapered cone/plug seacocks unlike a gate valve or ball valve, even a marine UL ball valve has dissimilar metals..
In this photo we can also see the dog washer flat spots. This dog washer rides around the valve body with the cone and the dog creates positive stops on either side. There are matching dogs cast into the body of the valve.
When re-installing the cone the flat spot should be facing up. This allows you to see the actual orientation of the valve hole by looking at the dog. The flat spot is in-line with the cone/plug hole and the valve body dogs are designed for this orientation at 12:00 when open.
If you install the dog upside down at 6:00 you will bend the dog on the valve body dogs as they are only machined flat on top and have a ramp or slope on the bottom that will bend an improperly installed dog washer.
All Spartan seacocks have dog washers and valve body stop dogs. Despite what many Cape Dory owners believe are Spartan seacocks they can often be Wilcox Crittenden seacocks. Cape Dory used WC seacocks when they ran out of Spartans or could not get them in time. If you don't have dog ear washers your valves are likely not Spartans.