artie & joemikeb:
All that's now totally moot.
I couldn't find anything that resembled my 'successful' clone — and CCC is a cool little app which allows for idiots like me to easily clone the HD — on my external HD; nothing which had a name that might indicate that it was something other than my TM backups.
When I tried to use Backup as my startup disk — and indeed assumed that if Backup showed up that such would indicate that identified a bootable volume therein — it refused to boot. So something odd was going on. I quit the process.
When I then rebooted from my main HD, the backup HD was toast. Disk Utility could recognize that it was there but could not mount the volume or repair it.
(Six-plus years is pretty good life for a little portable USB drive [WD My Passport], so I can't really bitch; I only wish it could've waited to crash until after all my planned upgrading and updating. But maybe it's all for the best that I had to start backups from scratch at this point.)
So ... I had to replace the backup drive. And now the oldest backup is today's.
It never rains, but it pours.
I haven't yet made another clone (it takes about an hour), so any suggestions as to how it can be tracked when it lands in my destination HD would be gratefully received.
