Wow that goes back a ways! If I recall
they made two models of the Crown toilet back in the day. The regular Crown was for use when it was mounted at or above the waterline. The Crown DD (Deep Draft) was for use below the waterline. I think the joker valve was the same but you can just call Raritan and ask them. They used to offer a trade
in on older Crown motor/pump assemblies. You send them your old toilet less the bowl plus money
and they send you a rebuilt or new replacement.
Kettlewell, I think we need a thread titled "The Proper use of Explosives in Marine
Sanitation Systems". Sounds like a Master's Thesis to me.