Thanks to everyone for the posts!  I did some more searching and found that the Garmin 60 and 76 are both equivalents with the same guts, software, etc.  The only difference appears to be in the case and buttons.  The 76 appears to have a larger case for the same weight, and it is the only one of Garmin's products that *they* claim floats.  Anybody used one?

Azalea:  Perhaps I've misjudged or mis-spoke.  About 30 years ago, I had an Apple II computer.  If I had kept it (and now I wish that I had!), it would, in all probability, still be functional.  But I doubt that I could get any service or software for it today.

It isn't so much the technology dies as it is that it gets forced out of use as it becomes "obsolete" and is no longer supported.  I believe the marketing term is "planned obsolescence".  Is this a problem with GPS devices?  A glance at Garmin's website finds "discontinued products".  Do they also discontinue support?

TCK