Anne — I am fairly certain that you have miscounted. Or, to put it another way, I think you counted the one with your finger on twice!
If you think about it, cutting tools and turntables were marked out in degrees; some perhaps with a lock that would only engage at a whole degree. Therefore you will find that virtually all counts of ribs or any other pattern are always a factor of 360. So, possible numbers are 2, 3, 4, 5, 6, 8, 10, 12, 15, 18, 20,
24, 30, 36, 45, 60, 72, 90, 120, 180, and 360.
Do you see the flaw in my argument? Arguably the most frequently used rib dip-mould was 16-rib, not in my list. Still, not too difficult to make, either by rotating by 22½° between each pattern, or by rotating 45° for the first eight patterns, and setting up again for the in-between patterns. 16 is the only mould pattern repeat I have found which is not in this list of factors.
... and your bowls are not Walsh.
Bernard C.
