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You might be thinking of the DW-5600E. It’s like the M5610 but without solar charging or the multi-band 6 radio sync. I much prefer the 5610 for those reasons but there are many more variants and colours of the non-solar 5600.
There is also the GW-B5600 line which is the “upgraded” 5600 that has Bluetooth along with solar and radio sync. This is the line that the metal cased models (GMW-B5000) are based on. Most of these are reversed LCD but currently there is a positive LCD version in a resin case in the range, the GW-B5600MG-1ER:
5610 - It's been on my wrist 80% of the time for the past 3 years.