New
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Towards the end of the last batch of insider previews the watermark was removed, signifying that the release is getting close to the final.
Now we have started a fresh batch the watermark has returned. Hope this helps explain it better.
Watermarks denote progress. Once a Landmark build is released, the Watermark is omitted.
The last few Insider builds that proceeded the RS1 or Redstone 1 update were themselves also RS1 builds but not RTM. Those latest were still developer builds that simply saw the watermark removed since they weren't the designated update while the activation status has a much longer extension then the other Preview type builds.
Now that the Redstone 1 is out the new builds forthcoming will be preparing over time for the next Redstone 2 and 3 updates scheduled to be seen in 2017. They could still see a name change however since the Threshold 2 last November was still only the first major update for 10. Never go specifically by number only since those change too frequently!
The previous posts signify the progression of developer builds seen until the major update is soon to be out where at that time the last few builds will not be seeing the usual watermark. Unlike what seen in years past between XP, Vista, 7 for sure the RC builds would still be seeing watermarks when following the beta builds. With MS doing away with service packs and incorporating most all updates into newer builds as well as changes made from gathering user feedback a new twist of temporarily not seeing the usual is something MS tossed into the mix.