Those ancestors, with a raw clay finish or glazed, were not called Bocarinas™ yet. I think they were named by Chris Schuermans' brand : the Clarytones™.
Here are 2 natural clay Clarytones™ which date from different times. The shapes already announce the Bocarina™, but certainly less refined.
Both wear the Schuermans' logo (see here for its explanation).
Besides the shapes, the main difference between those two models lays in the design of the nose saddles, which « were merely a result of the evolutionary process of improvement. The smaller one was the very 1st mould [Chris Schuermans] made (totally handmade). The larger one was (badly) designed with the aid of a computer. »
On the sound side, it is very difficult to give a global opinion. Indeed, those Clarytones™ were almost 100% hand made, without the regularity provided by the usage of a mould, contrarywise to the clay Bocarinas™ (see this topic) and for sure, to the plastic models. So, every nose flute was unique. More, and according to Chris Schuermans, the ones that are left are not necessary the best ones...
However, on both the following sound samples, you'll notice those flutes were much less precise than the clay and plastic Bocarinas™, and with a sound rather stifled and windy.
The first sample was recorded with the Delft blue Clarytone™, which is a very lazy nose flute, slow and fat in the sound producing.
The second sample is from the large raw clay Clarytone™, which is a rather « quick » and sharp instrument, allowing speedy notes.