My HRM-PRO had a baby

My first virtual run since 8.80 firmware and something rather odd showed up in my sensors list. Anyone seen this before or know what it is? I only have one strap.

This was on my home treadmill and I doubt there was another strap within range. No problem during the run. Just really weird to see this second entry with a rather unusual firmware version.

Note alpha firmware on the watch. Perhaps it's the watch that's at fault.

By the way, I've done lots of indoor bike rides with this combo and only one strap has been reported for the rides. I wonder if the virtual run and option for re-transmitted data might generate this little companion.