I am not supprised Jeff.
I only have seen one a few years back on ebay and the guy had the wrong name on it.
I don't think he knew what it was.
The kit was sold and imported by Polks back around 1980.
It was from a company in Italy called ISPD models.
I bought mine through Polks but it was also sold through Dynamic models who got them from Polks.
Here is a scan of the page from the 1981 Dynamic catalog that shows the kit.
The hull came in a clear plastic poly material.
You could basically build it clear if you wanted as is shown by the Dynamic add.
I remember seeing the same clear built boat at the big Polks store in NYC.
It used a ballast tank with a rubber membrane inside that expanded as the water was pumped in.
The top of the lower hull section had a steel sheet that you cemented to it that had three cutout sections.
There were covers that screwed down over the openings with rubber gaskets.
The boat was quite heavy for its size as it was a dry hull boat.
It was only semi scale and could be made to look like most WW2 subs.
Mine was painted like the Italian boats of the day.
I think they started life as Type 2 German boats.
Jeff may know more about that.
It was a cool boat for its day.