[beamn7]

That's the full time 4wd version..... It's a New Process 203 transfer case....
There is a 3rd differential in the T-Case, the LOC position locks it for absolute true 4wd making both driveshafts spin at the same speed. One of the biggest misconceptions is that this is a week T-case. Not so..... Had one in a 79 GMC K25 and did lots of plowing in MA with it. Worked great. Common for many folks to convert these to part time by either installing a kit in the t-case or manual hubs up front.
Stick with "HI" for normal driving, "LO" for low range 4wd and "LO LOC" for low range locked front and rear or "HI LOC" for high range locked. Either way, you have 4wd all the time.

Hope this helps. Sounds like you got a good deal!