Mine has arrived, many thanks Eddie.
I should have known exactly what I was getting because I've been wearing my 18A for the past month or so.
Differences that I can see are
1. The dial is more grey, perhaps just more matte.
2. The bezel insert is definitely more matte.
3. The digits are slightly smaller, as is the L symbol.
4. The minute hand is fractionally less long, although I wouldn't have noticed had I not been looking for it.
5. The bezel is more "gritty" and there is a tiny amount of backplay, but nothing to worry about.
6. The lume, with a very quick and unscientific test, glows slightly less powerfully, but probably perfectly adequately.
7. The case seems a little lighter in colour
The second hand was missing the markers by a mile on the way up earlier, it seems to have drifted round to the 5 a little now.
Overall I prefer the more matte look on the dial and bezel, but I think I prefer the larger digits.
A not very good photo