In fact, there is worldwide discussion about what these valveless instruments should be called. I am not an expert by any means, I just have a great interest and have worked hard enough to make most of the people that give me work playing a good reason to invite me back
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The CLARIN or CLARINO is a trumpet with mouthpiece, cylindrical tube and bell without valves or holes (vents). The notes playable are a predictable row based on the NATURAL partials (not overtones) that can be set up in the tube depending on the length of the horn. This makes it a NATURAL trumpet. The same would apply to the horn, making it a NATURAL HORN.
There are modern reproductions of these instruments although most modern players prefer a VENTED version. These vents are placed to correct tones that do not represent our modern sense of intonation or that are non-existant and only available through extreme lipping up or down.
Drilling holes in the tube is very much the same as in woodwind instruments. It changes the virtual length of the tube and allows a secondary set of tones. This is no longer NATURAL but much easier to play when balancing modern and baroque repertoires. Bob Barclay (a true expert) recommends calling these modern instruments (invented in the 1960s) BAROQUE TRUMPETS. It is safe to say that Bob Barclay has not gotten his way in the international community, although the definitions make sense.
These instruments, with or without vents, have a much different tone structure than modern instruments. They change the way you think about a Mozart Requiem or Beethoven symphony. The proficiency required to play Bach, Molter, Richter is another story however. It becomes obvious that this trumpet has NOTHING to do with modern instruments. A complete new skill set is required.
Modern trumpets are more "horn like" in that they are except for the valve block and tuning slide, primarily conical in shape. Natural/baroque trumpets are primarily cylindrical in shape. They also have a completely different mouthpiece - Longer than a conventional trumpet mouthpiece, a very sharp rim and a very sharp transition from the cup to the throat. A long conical backbore helps to tune the upper and lower octave.
Practicing a Bb trumpet with all the valves pushed down is quite different experience than playing on one of these "historical" instruments.
Does this help?