At 06:37 PM 1/13/2009 -0700, John Podeszwa in New Jersey wrote:
"In looking at the synchro rings for 2nd gear, one is brass and the other is steel. I know that the improved 2nd gear takes a steel ring. Okay, how do you tell which ring goes with which 2nd gear?

When you put the later steel synchro ring over the cone on the early gear they will touch face to face and provide no braking drag. That's why the steel ring does not work without the correct matching gear. When you put the early brass cone on the later gear the ring will sit high and proud of the surfaces of the gear. When you get them on the correct gears the both sit at about the same level around 0.030" to 0.040" apart face to face. I believe there is a difference in the cone angles, but I don't have the actual angle measurements at hand.

At 12:01 PM 11/6/2009 -0700, Tim Trevithick wrote:
"The modified steel type 2nd ring set up (often found in 'gold seal box's) is easy to visually I.D.   The cone on 2nd gear has a black ceramic like coating on it, so if it shines and has brass, it takes brass, but if it's black, brass is out of whack".

Addendum December 19, 2013:
The 2nd gear synchronizer ring was changed from brass to steel for MGB in 1965. This is a 22H249 Baulk Ring (steel) 2nd gear, and a 22H230 2nd Gear, for MGB (engine 18GB 31003 and later). Notice the steel ring is being held with a magnet while taking the picture. Picture is courtesy of Del Rawlins in Anchorage, Alaska, USA.

The steel ring and mating gear can be used to upgrade an earlier MGB or MGA gearbox. The heat treated steel ring will commonly have a light yellow color as in the picture. Some parts may otherwise be dull gray (depending on the steel alloy and heat treating process). The proper mating gear will have a black ceramic like coating on the cone surface.

The steel ring must be used with the coated gear. The brass ring must be used with the non-coated gear. I have been told that the later gear has same dimensions as the earlier gear, although the coating may add some thickness to the cone surface. When in doubt, check the ring with a magnet. Also test fit the ring to the gear before installation in the gearbox. There should be a space of 0.030" to 0.040" between the ring and mating face of the gear. At 0.020" space it will still work and may be put back in service. If the space is zero (ring touching face of the gear), then the synchronizer will definitely not work.