The picture from Q&A L006 shows a sailing dinghy with national letters and sail numbers applied in accordance with the spacing, dimensional and positioning requirements of the RRS.
 

Do the sail numbers comply with the requirements of rule G1.2(a)’s last sentence?

Rule G1.2(a)’s last sentence does not state any requirement at all. Rule G1.2(a) requires the numbers to be clearly legible and of the same colour, but it does not require a commercially available type face to be used. The last sentence just advices what kind of commercially available typefaces are acceptable.

Given that Helvetica clearly identifies a difference between the digits 2 and 5, and does not cause confusion in reversing the sail number (show through from one side of the sail to the other); does the typeface used in the picture from Q&A provide equal or better legibility than Helvetica and therefore is this an acceptable typeface for use as per rule G1.2(a)?

Answer 2

Note that the rules of an ISAF class may change rule G1.2 (see rule G5).