Just wanted to follow up on this. In addition to posting here, I also contacted the James Avery company and received the following response:
Thank you for your interest in our Martin Luther Wedding Band.
There were originally two bands. The WB-27 (still active) is slightly wider, and has a 4 mm gemstone. The WB-27S was slightly more narrow, and had a 3mm gemstone. Both were originated in the early 1980s; the WB-27S was retired in 2007.
If you are seeking further information, we would be able to provide you with:
--Meaning or symbolism of the item, when applicable
--Designer
--Year Released
--Last Current Price with Date
Due to the high volume of requests from customers to identify designs and the labor to research this information in our archives, it has become necessary to charge a research fee of $12.00 for this service. If you are interested, you may call us at 1-800-283-1770 with payment information and refer to this email; we would be happy to research and provide you with further information.
I'm still not 100% sure which version of the ring I have. The gemstone on mine is about 3.5 mm across, maybe a little less, so I'm not very sure which design that would fall under. I also don't know how wide the bands for either ring are supposed to be (perhaps I'll google it and see what I can discover). But whatevs – it's a pretty neat ring, and now I know more about it than I did to begin with. :)