G' Day Ian,
Dave's answer is correct. Your question made me go back and review history a bit. The answer goes back to the original GQ III which came out in 2006. That had the original Turn Indicator with 10 ticks for changing course 180°. When FAI was published, we switched to the newer Turn Indicator featuring compass points, where each tick mark is two points (11.25° x 2 = 22.5°) and eight two point ticks equal 180° ( 22.5° x 8 = 180°). This provides a "saltier" feel using the traditional maritime terms for changing course and is a little better simulation of making turns.
Many years ago, I posted two amendments to GQ III:
Amendment 1 included the new compass point version of the Turn Indicator.
Amendment 2 added the "back" of the indicator with torpedo gyro arcs for making torpedo attacks along with the change in the torpedo attack procedure. The new method was first featured in FAI as an alternative way to make torpedo attacks. It proved much better and we revised GQ III accordingly as part of Amendment 2. The gyro angles reverse side of the Turn Indicator was updated with additional, but narrower arcs to better reflect the bigger torpedo spreads used in WW II and the greater ranges employed.
With Amendment 2, the Turn Indicator reached its current form and remains in use today and is also employed in the optional acrylic Turn Indicators available from ODGW which are used by many gamers. Back when the amendments were issued, gratis download pdf files were made available to registered owners of the GQ III rules with change pages and revised charts. Then in 2012, some small additional revisions were added. Rather than making another amendment, I took some time and went back and compiled the amendments and new changes into a consolidated set which we made available as GQ 3.3 in 2012.
If you are still using the original GQ III rules, you might want to consider getting a copy of GQ 3.3 which consolides everything in one package and brings you current. Needless to say, the updated Turn Indicator graphics and changes to other charts and tables are included in this consolidated package. Also, you will note on the ODGW website that there are a number of free download supplements available for other WW II navies. If you don't want to choose that course, send me your e-mail address and I will forwards a pdf of the updated Turn Indicators directly to you.
Fair winds,
LONNIE