Further comment WRT Seiko and model numbering, and how they do themselves NO favor.
Seiko has numerous models allowing atomic time sync via RF reception. They generally were split into 3 lines, depending on finish levels; they shared the same movement, for the most part. That's OK; one line was basic, one sporty, one more dressy. The Spirit Smart was the basic...galvanized dials, I believe, simplest cases. Most of them are SBTM xxx.
The KILLER part is...these started with models that only received the Japanese signal. (It's on a different frequency.) As of a couple years ago...they came out with models that received signals from Japan, the US, and Germany. BOTH using the SBTM numbering. For quite a while, they were both heavily represented in the catalog. I *believe* that the movement model numbers were even the same, but I may be mis-remembering. If you knew what you were looking for, the dial made it clear...but that was it.
Spirit contains both mechanical and quartz. Argh. Spirit Smart is all solar...but some are RF, some aren't. SBTM is all RF. OK...until you get into the Japan-only vs. international line. Then looking at the other major Spirit Smart...solar but not RF. 10 models show, 9 of which have 2 subdial areas, at 12 and 6...meaning the single 3-hander is something of an orphan. 7 of the 9 are SPBJ; the other 2 are SPBY. The SPBYs are chronographs with tachymeter scale...ok. The SPBJs...5 are world time, 2 are perpetual calendar. But ALL 9 are fundamentally highly similar, with 2 major subdials at 12 and 6, and a small, subtle subdial at 9.
But you've really got to look to tell which is which. And this is not new; you can readily find criticism about their inconsistent branding in their product lines going back quite a ways.