Shimano Nexus 3 speed decal interpretation

[Brad B Rad]

G'day folks, I have a question about the numerical decal on my Shimano Nexus 3 speed hub. I have 2 wheel sets with this hub. They both have a little round white decal, one has 20 and the other has 21. Is this the number of teeth on the cog? As the 20 does have a 20 tooth however the 21 has an 18 tooth. I got them 2nd hand so I guess the cog could have been swapped out. Both are on 700c rims and both bikes are just entry level commuters.
I do have pictures but I can't see any upload option here. I guess if you know these hubs you'll know what I'm talking about anyway.
Thanks in advance.

[P!N20]

Thought it was just the quality control number.

[Duck!]

^^^ That would be my thought too, or something along similar lines. The hubs are usually shipped without a sprocket to allow fine tuning of the drive ratio to suit the type of bike they're going in.

[Brad B Rad]

Ok, thanks Pin20 and Duck, that does seem like a logical explanation.