It's a GPSMap 78sc. Can't recall
what year, but I'd guess I bought it at least 3-4 years ago.*
According to the Setup - About screen:
Software version 5.40
To modify displays is certainly bnot intuitive. You need to play around with Garmins quite a bit before you start to make sense of how the setup screens work.
Here's how to do it:
Scroll to the Compass page
1. Hit MENU once.
2. Scroll down to "Change Dashboard"
3. Hit ENTER.
4. Scroll to "Large Data Field" and hit ENTER
That puts you back on the Compass page with one large data field showing.
5. Hit MENU again.
6. Scroll to "Change Data Fields"
7. Hit ENTER.
That returns to the Compass page with the first (in this case only) data field highlighted (in a sort of light brown).
8. Hit ENTER again
9. Scroll to "Locations(lat/lon)"
10. Hit ENTER once more
That again returns to the Compass page.
11. Now hit QUIT to get out of the editing mode.
Another possible place to do similar is the Trip Computer page.
Follow the same instructions as above, but after step 4, you will see three data fields with the first one selected. Select each one in turn by and follow the above process to make it show whatever you want. (Speed, heading and Location are quite a useful combination)
*Edit - just checked my laptop
and I installed Homeport in Jun 2012, so I definitely bought the 78sc more than 4 years ago.